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There are over 3700 types of mosquitoes worldwide and over 200 types in the continental United States, of which only 12 are associated with transmitting diseases to humans. The majority are just a nuisance. Since they cannot readily be distinguished, strategies to prevent any bites are recommended.
West Nile Virus
In the US, West Nile virus (WNV) is the leading cause of neuroinvasive arboviral disease. Just hearing the name took me back to New York in 1999 when sightings of dead birds around the city and boroughs were reported daily. The virus was isolated that same year. The enzootic circle occurs between mosquitoes and birds, which are the primary vertebrate host via the bite of Culex mosquitoes. After a bite from an infected mosquito, humans are usually a dead-end host since the level and duration of viremia needed to infect another mosquito is insufficient.
Human-to-human transmission is documented through blood transfusion and solid organ transplantation. Vertical transmission is rarely described. Initially isolated in New York, WNV quickly spread across North America and has been isolated in every continent except Antarctica. Most cases occur in the summer and autumn.
Most infected individuals are asymptomatic. Those who do develop symptoms have fever, headache, myalgia, arthralgia, nausea, vomiting, and a transient rash. Less than 1% develop meningitis/encephalitis symptoms similar to other causes of aseptic meningitis. Those with encephalitis in addition to fever and headache may have altered mental status and focal neurologic deficits including flaccid paralysis or movement disorders.
Detection of anti-WNV IgM antibodies (AB) in serum or CSF is the most common way to make the diagnosis. IgM AB usually is present within 3-8 days after onset of symptoms and persists up to 90 days. Data from ArboNET, the national arboviral surveillance system managed by Centers for Disease Control and Prevention and state health departments, reveal that from 1999 to 2022 there were 56,575 cases of WNV including 28,684 cases of neuroinvasive disease. In 2023 there were 2,406 and 1,599 cases, respectively. Those historic totals for WNV are 10 times greater than the totals for all the other etiologies of neuroinvasive arboviral diseases in the US combined (Jamestown Canyon, LaCrosse, St. Louis, and Eastern Equine encephalitis n = 1813).
Remember to include WNV in your differential of a febrile patient with neurologic symptoms, mosquito bites, blood transfusions, and organ transplantation. Treatment is supportive care.
The US began screening all blood donations for WNV in 2003. Organ donor screening is not universal.
Dengue
Dengue, another arbovirus, is transmitted by bites of infected Aedes aegypti and Aedes albopictus mosquitoes, which prefer to feed during the daytime. There are four dengue virus serotypes: DENV-1 DENV-2, DENV-3 and DENV-4. In endemic areas, all four serotypes are usually co-circulating and people can be infected by each one.
Long-term immunity is type specific. Heterologous protection lasts only a few months. Dengue is endemic throughout the tropics and subtropics of Asia, Africa, and the Americas. Approximately 53% of the world’s population live in an area where dengue transmission can occur. In the US, most cases are reported from Puerto Rico. Dengue is endemic in the following US territories: Puerto Rico, US Virgin Islands, American Samoa, and free associated states. Most cases reported on the mainland are travel related. However, locally acquired dengue has been reported. From 2010 to 2023 Hawaii reported 250 cases, Florida 438, and Texas 40 locally acquired cases. During that same period, Puerto Rico reported more than 32,000 cases. It is the leading cause of febrile illness for travelers returning from the Caribbean, Latin America, and South Asia.Peru is currently experiencing an outbreak with more than 25,000 cases reported since January 2024. Most cases of dengue occur in adolescents and young adults. Severe disease occurs most often in infants, those with underlying chronic disease, pregnant women, and persons infected with dengue for the second time.
Symptoms range from a mild febrile illness to severe disease associated with hemorrhage and shock. Onset is usually 7-10 days after infection and symptoms include high fever, severe headache, retro-orbital pain, arthralgia and myalgias, nausea, and vomiting; some may develop a generalized rash.
The World Health Organization (WHO) classifies dengue as 1) dengue with or without warning signs for progression of disease and 2) severe dengue. Warning signs for disease progression include abdominal pain or tenderness, persistent vomiting, fluid accumulation (e.g., ascites, pericardial or pleural effusion), mucosal bleeding, restlessness, postural hypotension, liver enlargement greater than 2 cm. Severe dengue is defined as any sign of severe plasma leakage leading to shock, severe bleeding or organ failure, or fluid accumulation with respiratory distress. Management is supportive care.
Prevention: In the US, Dengvaxia, a live attenuated tetravalent vaccine, is approved for use in children aged 9–16 years with laboratory-confirmed previous dengue virus infection and living in areas where dengue is endemic. It is administered at 0, 6, and 12 months. It is not available for purchase on the mainland. Continued control of the vector and personal protection is necessary to prevent recurrent infections.
CHIKV
Chikungunya (CHIKV), which means “that which bends up” in the Mkonde language of Tanzania, refers to the appearance of the person with severe usually symmetric arthralgias characteristic for this infection that otherwise is often clinically confused with dengue and Zika. It too is transmitted by A. aegypti and A. albopictus and is prevalent in tropical Africa, Asia, Central and South America, and the Caribbean. Like dengue it is predominantly an urban disease. The WHO reported the first case in the Western Hemisphere in Saint Martin in December 2013. By August 2014, 31 additional territories and Caribbean or South American countries reported 576,535 suspected cases.Florida first reported locally acquired CHIKV in June 2014. By December an additional 11 cases had been identified. Texas reported one case in 2015. Diagnosis is with IgM ab or PCR. Treatment is supportive with most recovering from acute illness within 2 weeks. Data in adults indicate 40-52% may develop chronic or recurrent joint pain.
Prevention: IXCHIQ, a live attenuated vaccine, was licensed in November 2023 and recommended by the CDC in February 2024 for use in persons at least 18 years of age with travel to destinations where there is a CHIKV outbreak. It may be considered for persons traveling to a country or territory without an outbreak but with evidence of CHIKV transmission among humans within the last 5 years and those staying in endemic areas for a cumulative period of at least 6 months over a 2-year period. Specific recommendations for lab workers and persons older than 65 years were also made. This is good news for your older patients who may be participating in mission trips, volunteering, studying abroad, or just vacationing in an endemic area. Adolescent vaccine trials are ongoing and pediatric trials will soon be initiated. In addition, vector control and use of personal protective measures cannot be emphasized enough.
There are several other mosquito borne diseases, however our discussion here is limited to three. Why these three? WNV as a reminder that it is the most common neuroinvasive agent in the US. Dengue and CHIKV because they are not endemic in the US so they might not routinely be considered in febrile patients; both diseases have been reported and acquired on the mainland and your patients may travel to an endemic area and return home with an unwanted souvenir. You will be ready for them.
Dr. Word is a pediatric infectious disease specialist and director of the Houston Travel Medicine Clinic. She said she had no relevant financial disclosures.
Suggested Reading
Chikungunya. Centers for Disease Control and Prevention. 2024. https://www.cdc.gov/vaccines/acip/recommendations.html.
Fagrem AC et al. West Nile and Other Nationally Notifiable Arboviral Diseases–United States, 2021. MMWR Morb Mortal Wkly Rep. 2023 Aug 25;72(34):901-906.
Fever in Returned Travelers, Travel Medicine (Fourth Edition). 2019. doi: 10.1016/B978-0-323-54696-6.00056-2.
Paz-Baily et al. Dengue Vaccine: Recommendations of the Advisory Committee on Immunization Practices, United States, 2021 MMWR Recomm Rep. 2021 Dec 17;70(6):1-16).
Staples JE and Fischer M. Chikungunya virus in the Americas — what a vectorborne pathogen can do. N Engl J Med. 2014 Sep 4;371(10):887-9.
Mosquitoes and Diseases A-Z, Centers for Disease Control and Prevention. https://www.cdc.gov/mosquitoes/about/diseases.html.
There are over 3700 types of mosquitoes worldwide and over 200 types in the continental United States, of which only 12 are associated with transmitting diseases to humans. The majority are just a nuisance. Since they cannot readily be distinguished, strategies to prevent any bites are recommended.
West Nile Virus
In the US, West Nile virus (WNV) is the leading cause of neuroinvasive arboviral disease. Just hearing the name took me back to New York in 1999 when sightings of dead birds around the city and boroughs were reported daily. The virus was isolated that same year. The enzootic circle occurs between mosquitoes and birds, which are the primary vertebrate host via the bite of Culex mosquitoes. After a bite from an infected mosquito, humans are usually a dead-end host since the level and duration of viremia needed to infect another mosquito is insufficient.
Human-to-human transmission is documented through blood transfusion and solid organ transplantation. Vertical transmission is rarely described. Initially isolated in New York, WNV quickly spread across North America and has been isolated in every continent except Antarctica. Most cases occur in the summer and autumn.
Most infected individuals are asymptomatic. Those who do develop symptoms have fever, headache, myalgia, arthralgia, nausea, vomiting, and a transient rash. Less than 1% develop meningitis/encephalitis symptoms similar to other causes of aseptic meningitis. Those with encephalitis in addition to fever and headache may have altered mental status and focal neurologic deficits including flaccid paralysis or movement disorders.
Detection of anti-WNV IgM antibodies (AB) in serum or CSF is the most common way to make the diagnosis. IgM AB usually is present within 3-8 days after onset of symptoms and persists up to 90 days. Data from ArboNET, the national arboviral surveillance system managed by Centers for Disease Control and Prevention and state health departments, reveal that from 1999 to 2022 there were 56,575 cases of WNV including 28,684 cases of neuroinvasive disease. In 2023 there were 2,406 and 1,599 cases, respectively. Those historic totals for WNV are 10 times greater than the totals for all the other etiologies of neuroinvasive arboviral diseases in the US combined (Jamestown Canyon, LaCrosse, St. Louis, and Eastern Equine encephalitis n = 1813).
Remember to include WNV in your differential of a febrile patient with neurologic symptoms, mosquito bites, blood transfusions, and organ transplantation. Treatment is supportive care.
The US began screening all blood donations for WNV in 2003. Organ donor screening is not universal.
Dengue
Dengue, another arbovirus, is transmitted by bites of infected Aedes aegypti and Aedes albopictus mosquitoes, which prefer to feed during the daytime. There are four dengue virus serotypes: DENV-1 DENV-2, DENV-3 and DENV-4. In endemic areas, all four serotypes are usually co-circulating and people can be infected by each one.
Long-term immunity is type specific. Heterologous protection lasts only a few months. Dengue is endemic throughout the tropics and subtropics of Asia, Africa, and the Americas. Approximately 53% of the world’s population live in an area where dengue transmission can occur. In the US, most cases are reported from Puerto Rico. Dengue is endemic in the following US territories: Puerto Rico, US Virgin Islands, American Samoa, and free associated states. Most cases reported on the mainland are travel related. However, locally acquired dengue has been reported. From 2010 to 2023 Hawaii reported 250 cases, Florida 438, and Texas 40 locally acquired cases. During that same period, Puerto Rico reported more than 32,000 cases. It is the leading cause of febrile illness for travelers returning from the Caribbean, Latin America, and South Asia.Peru is currently experiencing an outbreak with more than 25,000 cases reported since January 2024. Most cases of dengue occur in adolescents and young adults. Severe disease occurs most often in infants, those with underlying chronic disease, pregnant women, and persons infected with dengue for the second time.
Symptoms range from a mild febrile illness to severe disease associated with hemorrhage and shock. Onset is usually 7-10 days after infection and symptoms include high fever, severe headache, retro-orbital pain, arthralgia and myalgias, nausea, and vomiting; some may develop a generalized rash.
The World Health Organization (WHO) classifies dengue as 1) dengue with or without warning signs for progression of disease and 2) severe dengue. Warning signs for disease progression include abdominal pain or tenderness, persistent vomiting, fluid accumulation (e.g., ascites, pericardial or pleural effusion), mucosal bleeding, restlessness, postural hypotension, liver enlargement greater than 2 cm. Severe dengue is defined as any sign of severe plasma leakage leading to shock, severe bleeding or organ failure, or fluid accumulation with respiratory distress. Management is supportive care.
Prevention: In the US, Dengvaxia, a live attenuated tetravalent vaccine, is approved for use in children aged 9–16 years with laboratory-confirmed previous dengue virus infection and living in areas where dengue is endemic. It is administered at 0, 6, and 12 months. It is not available for purchase on the mainland. Continued control of the vector and personal protection is necessary to prevent recurrent infections.
CHIKV
Chikungunya (CHIKV), which means “that which bends up” in the Mkonde language of Tanzania, refers to the appearance of the person with severe usually symmetric arthralgias characteristic for this infection that otherwise is often clinically confused with dengue and Zika. It too is transmitted by A. aegypti and A. albopictus and is prevalent in tropical Africa, Asia, Central and South America, and the Caribbean. Like dengue it is predominantly an urban disease. The WHO reported the first case in the Western Hemisphere in Saint Martin in December 2013. By August 2014, 31 additional territories and Caribbean or South American countries reported 576,535 suspected cases.Florida first reported locally acquired CHIKV in June 2014. By December an additional 11 cases had been identified. Texas reported one case in 2015. Diagnosis is with IgM ab or PCR. Treatment is supportive with most recovering from acute illness within 2 weeks. Data in adults indicate 40-52% may develop chronic or recurrent joint pain.
Prevention: IXCHIQ, a live attenuated vaccine, was licensed in November 2023 and recommended by the CDC in February 2024 for use in persons at least 18 years of age with travel to destinations where there is a CHIKV outbreak. It may be considered for persons traveling to a country or territory without an outbreak but with evidence of CHIKV transmission among humans within the last 5 years and those staying in endemic areas for a cumulative period of at least 6 months over a 2-year period. Specific recommendations for lab workers and persons older than 65 years were also made. This is good news for your older patients who may be participating in mission trips, volunteering, studying abroad, or just vacationing in an endemic area. Adolescent vaccine trials are ongoing and pediatric trials will soon be initiated. In addition, vector control and use of personal protective measures cannot be emphasized enough.
There are several other mosquito borne diseases, however our discussion here is limited to three. Why these three? WNV as a reminder that it is the most common neuroinvasive agent in the US. Dengue and CHIKV because they are not endemic in the US so they might not routinely be considered in febrile patients; both diseases have been reported and acquired on the mainland and your patients may travel to an endemic area and return home with an unwanted souvenir. You will be ready for them.
Dr. Word is a pediatric infectious disease specialist and director of the Houston Travel Medicine Clinic. She said she had no relevant financial disclosures.
Suggested Reading
Chikungunya. Centers for Disease Control and Prevention. 2024. https://www.cdc.gov/vaccines/acip/recommendations.html.
Fagrem AC et al. West Nile and Other Nationally Notifiable Arboviral Diseases–United States, 2021. MMWR Morb Mortal Wkly Rep. 2023 Aug 25;72(34):901-906.
Fever in Returned Travelers, Travel Medicine (Fourth Edition). 2019. doi: 10.1016/B978-0-323-54696-6.00056-2.
Paz-Baily et al. Dengue Vaccine: Recommendations of the Advisory Committee on Immunization Practices, United States, 2021 MMWR Recomm Rep. 2021 Dec 17;70(6):1-16).
Staples JE and Fischer M. Chikungunya virus in the Americas — what a vectorborne pathogen can do. N Engl J Med. 2014 Sep 4;371(10):887-9.
Mosquitoes and Diseases A-Z, Centers for Disease Control and Prevention. https://www.cdc.gov/mosquitoes/about/diseases.html.
There are over 3700 types of mosquitoes worldwide and over 200 types in the continental United States, of which only 12 are associated with transmitting diseases to humans. The majority are just a nuisance. Since they cannot readily be distinguished, strategies to prevent any bites are recommended.
West Nile Virus
In the US, West Nile virus (WNV) is the leading cause of neuroinvasive arboviral disease. Just hearing the name took me back to New York in 1999 when sightings of dead birds around the city and boroughs were reported daily. The virus was isolated that same year. The enzootic circle occurs between mosquitoes and birds, which are the primary vertebrate host via the bite of Culex mosquitoes. After a bite from an infected mosquito, humans are usually a dead-end host since the level and duration of viremia needed to infect another mosquito is insufficient.
Human-to-human transmission is documented through blood transfusion and solid organ transplantation. Vertical transmission is rarely described. Initially isolated in New York, WNV quickly spread across North America and has been isolated in every continent except Antarctica. Most cases occur in the summer and autumn.
Most infected individuals are asymptomatic. Those who do develop symptoms have fever, headache, myalgia, arthralgia, nausea, vomiting, and a transient rash. Less than 1% develop meningitis/encephalitis symptoms similar to other causes of aseptic meningitis. Those with encephalitis in addition to fever and headache may have altered mental status and focal neurologic deficits including flaccid paralysis or movement disorders.
Detection of anti-WNV IgM antibodies (AB) in serum or CSF is the most common way to make the diagnosis. IgM AB usually is present within 3-8 days after onset of symptoms and persists up to 90 days. Data from ArboNET, the national arboviral surveillance system managed by Centers for Disease Control and Prevention and state health departments, reveal that from 1999 to 2022 there were 56,575 cases of WNV including 28,684 cases of neuroinvasive disease. In 2023 there were 2,406 and 1,599 cases, respectively. Those historic totals for WNV are 10 times greater than the totals for all the other etiologies of neuroinvasive arboviral diseases in the US combined (Jamestown Canyon, LaCrosse, St. Louis, and Eastern Equine encephalitis n = 1813).
Remember to include WNV in your differential of a febrile patient with neurologic symptoms, mosquito bites, blood transfusions, and organ transplantation. Treatment is supportive care.
The US began screening all blood donations for WNV in 2003. Organ donor screening is not universal.
Dengue
Dengue, another arbovirus, is transmitted by bites of infected Aedes aegypti and Aedes albopictus mosquitoes, which prefer to feed during the daytime. There are four dengue virus serotypes: DENV-1 DENV-2, DENV-3 and DENV-4. In endemic areas, all four serotypes are usually co-circulating and people can be infected by each one.
Long-term immunity is type specific. Heterologous protection lasts only a few months. Dengue is endemic throughout the tropics and subtropics of Asia, Africa, and the Americas. Approximately 53% of the world’s population live in an area where dengue transmission can occur. In the US, most cases are reported from Puerto Rico. Dengue is endemic in the following US territories: Puerto Rico, US Virgin Islands, American Samoa, and free associated states. Most cases reported on the mainland are travel related. However, locally acquired dengue has been reported. From 2010 to 2023 Hawaii reported 250 cases, Florida 438, and Texas 40 locally acquired cases. During that same period, Puerto Rico reported more than 32,000 cases. It is the leading cause of febrile illness for travelers returning from the Caribbean, Latin America, and South Asia.Peru is currently experiencing an outbreak with more than 25,000 cases reported since January 2024. Most cases of dengue occur in adolescents and young adults. Severe disease occurs most often in infants, those with underlying chronic disease, pregnant women, and persons infected with dengue for the second time.
Symptoms range from a mild febrile illness to severe disease associated with hemorrhage and shock. Onset is usually 7-10 days after infection and symptoms include high fever, severe headache, retro-orbital pain, arthralgia and myalgias, nausea, and vomiting; some may develop a generalized rash.
The World Health Organization (WHO) classifies dengue as 1) dengue with or without warning signs for progression of disease and 2) severe dengue. Warning signs for disease progression include abdominal pain or tenderness, persistent vomiting, fluid accumulation (e.g., ascites, pericardial or pleural effusion), mucosal bleeding, restlessness, postural hypotension, liver enlargement greater than 2 cm. Severe dengue is defined as any sign of severe plasma leakage leading to shock, severe bleeding or organ failure, or fluid accumulation with respiratory distress. Management is supportive care.
Prevention: In the US, Dengvaxia, a live attenuated tetravalent vaccine, is approved for use in children aged 9–16 years with laboratory-confirmed previous dengue virus infection and living in areas where dengue is endemic. It is administered at 0, 6, and 12 months. It is not available for purchase on the mainland. Continued control of the vector and personal protection is necessary to prevent recurrent infections.
CHIKV
Chikungunya (CHIKV), which means “that which bends up” in the Mkonde language of Tanzania, refers to the appearance of the person with severe usually symmetric arthralgias characteristic for this infection that otherwise is often clinically confused with dengue and Zika. It too is transmitted by A. aegypti and A. albopictus and is prevalent in tropical Africa, Asia, Central and South America, and the Caribbean. Like dengue it is predominantly an urban disease. The WHO reported the first case in the Western Hemisphere in Saint Martin in December 2013. By August 2014, 31 additional territories and Caribbean or South American countries reported 576,535 suspected cases.Florida first reported locally acquired CHIKV in June 2014. By December an additional 11 cases had been identified. Texas reported one case in 2015. Diagnosis is with IgM ab or PCR. Treatment is supportive with most recovering from acute illness within 2 weeks. Data in adults indicate 40-52% may develop chronic or recurrent joint pain.
Prevention: IXCHIQ, a live attenuated vaccine, was licensed in November 2023 and recommended by the CDC in February 2024 for use in persons at least 18 years of age with travel to destinations where there is a CHIKV outbreak. It may be considered for persons traveling to a country or territory without an outbreak but with evidence of CHIKV transmission among humans within the last 5 years and those staying in endemic areas for a cumulative period of at least 6 months over a 2-year period. Specific recommendations for lab workers and persons older than 65 years were also made. This is good news for your older patients who may be participating in mission trips, volunteering, studying abroad, or just vacationing in an endemic area. Adolescent vaccine trials are ongoing and pediatric trials will soon be initiated. In addition, vector control and use of personal protective measures cannot be emphasized enough.
There are several other mosquito borne diseases, however our discussion here is limited to three. Why these three? WNV as a reminder that it is the most common neuroinvasive agent in the US. Dengue and CHIKV because they are not endemic in the US so they might not routinely be considered in febrile patients; both diseases have been reported and acquired on the mainland and your patients may travel to an endemic area and return home with an unwanted souvenir. You will be ready for them.
Dr. Word is a pediatric infectious disease specialist and director of the Houston Travel Medicine Clinic. She said she had no relevant financial disclosures.
Suggested Reading
Chikungunya. Centers for Disease Control and Prevention. 2024. https://www.cdc.gov/vaccines/acip/recommendations.html.
Fagrem AC et al. West Nile and Other Nationally Notifiable Arboviral Diseases–United States, 2021. MMWR Morb Mortal Wkly Rep. 2023 Aug 25;72(34):901-906.
Fever in Returned Travelers, Travel Medicine (Fourth Edition). 2019. doi: 10.1016/B978-0-323-54696-6.00056-2.
Paz-Baily et al. Dengue Vaccine: Recommendations of the Advisory Committee on Immunization Practices, United States, 2021 MMWR Recomm Rep. 2021 Dec 17;70(6):1-16).
Staples JE and Fischer M. Chikungunya virus in the Americas — what a vectorborne pathogen can do. N Engl J Med. 2014 Sep 4;371(10):887-9.
Mosquitoes and Diseases A-Z, Centers for Disease Control and Prevention. https://www.cdc.gov/mosquitoes/about/diseases.html.
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<root generator="drupal.xsl" gversion="1.7"> <header> <fileName>167258</fileName> <TBEID>0C04EFB6.SIG</TBEID> <TBUniqueIdentifier>MD_0C04EFB6</TBUniqueIdentifier> <newsOrJournal>News</newsOrJournal> <publisherName>Frontline Medical Communications</publisherName> <storyname>ID Consult: Mosquitoes</storyname> <articleType>2</articleType> <TBLocation>QC Done-All Pubs</TBLocation> <QCDate>20240318T132834</QCDate> <firstPublished>20240318T132930</firstPublished> <LastPublished>20240318T132930</LastPublished> <pubStatus qcode="stat:"/> <embargoDate/> <killDate/> <CMSDate>20240318T132930</CMSDate> <articleSource/> <facebookInfo/> <meetingNumber/> <byline>Bonnie M. Word, MD</byline> <bylineText>BONNIE M. WORD, MD </bylineText> <bylineFull>BONNIE M. WORD, MD </bylineFull> <bylineTitleText/> <USOrGlobal/> <wireDocType/> <newsDocType>Column</newsDocType> <journalDocType/> <linkLabel/> <pageRange/> <citation/> <quizID/> <indexIssueDate/> <itemClass qcode="ninat:text"/> <provider qcode="provider:imng"> <name>IMNG Medical Media</name> <rightsInfo> <copyrightHolder> <name>Frontline Medical News</name> </copyrightHolder> <copyrightNotice>Copyright (c) 2015 Frontline Medical News, a Frontline Medical Communications Inc. company. All rights reserved. This material may not be published, broadcast, copied, or otherwise reproduced or distributed without the prior written permission of Frontline Medical Communications Inc.</copyrightNotice> </rightsInfo> </provider> <abstract/> <metaDescription>There are over 3700 types of mosquitoes worldwide and over 200 types in the continental United States, of which only 12 are associated with transmitting disease</metaDescription> <articlePDF/> <teaserImage>290230</teaserImage> <teaser>Because some mosquitoes can carry and transmit infectious diseases, prevention of bites is important, as is recognition of mosquito-borne illnesses. </teaser> <title>Summertime and Mosquitoes Are Breeding</title> <deck/> <disclaimer/> <AuthorList/> <articleURL/> <doi/> <pubMedID/> <publishXMLStatus/> <publishXMLVersion>1</publishXMLVersion> <useEISSN>0</useEISSN> <urgency/> <pubPubdateYear>2024</pubPubdateYear> <pubPubdateMonth/> <pubPubdateDay/> <pubVolume/> <pubNumber/> <wireChannels/> <primaryCMSID/> <CMSIDs/> <keywords/> <seeAlsos/> <publications_g> <publicationData> <publicationCode>FP</publicationCode> <pubIssueName/> <pubArticleType/> <pubTopics/> <pubCategories/> <pubSections/> <journalTitle/> <journalFullTitle/> <copyrightStatement>Copyright 2017 Frontline Medical News</copyrightStatement> </publicationData> <publicationData> <publicationCode>PN</publicationCode> <pubIssueName/> <pubArticleType/> <pubTopics/> <pubCategories/> <pubSections/> <journalTitle/> <journalFullTitle/> <copyrightStatement/> </publicationData> <publicationData> <publicationCode>idprac</publicationCode> <pubIssueName/> <pubArticleType/> <pubTopics/> <pubCategories/> <pubSections/> </publicationData> </publications_g> <publications> <term>15</term> <term canonical="true">25</term> <term>20</term> </publications> <sections> <term canonical="true">80</term> <term>39313</term> </sections> <topics> <term canonical="true">234</term> <term>271</term> </topics> <links> <link> <itemClass qcode="ninat:picture"/> <altRep contenttype="image/jpeg">images/24011434.jpg</altRep> <description role="drol:caption"/> <description role="drol:credit">Wikimedia Commons/Muhammad Mahdi Karim/Creative Commons License</description> </link> <link> <itemClass qcode="ninat:picture"/> <altRep contenttype="image/jpeg">images/2400fff9.jpg</altRep> <description role="drol:caption">Dr. Bonnie M. Word</description> <description role="drol:credit"/> </link> </links> </header> <itemSet> <newsItem> <itemMeta> <itemRole>Main</itemRole> <itemClass>text</itemClass> <title>Summertime and Mosquitoes Are Breeding</title> <deck/> </itemMeta> <itemContent> <p>There are over 3700 types of mosquitoes worldwide and over 200 types in the continental United States, of which only 12 are associated with transmitting diseases to humans. The majority are just a nuisance. Since they cannot readily be distinguished, strategies to prevent any bites are recommended. </p> <h2>West Nile Virus</h2> <p>In the US, West Nile virus (WNV) is the leading cause of neuroinvasive arboviral disease. Just hearing the name took me back to New York in 1999 when sightings of dead birds around the city and boroughs were reported daily. The virus was isolated that same year. The enzootic circle occurs between mosquitoes and birds, which are the primary vertebrate host via the bite of Culex mosquitoes. After a bite from an infected mosquito, humans are usually a dead-end host since the level and duration of viremia needed to infect another mosquito is insufficient. </p> <p>Human-to-human transmission is documented through blood transfusion and solid organ transplantation. Vertical transmission is rarely described. Initially isolated in New York, WNV quickly spread across North America and has been isolated in every continent except Antarctica. Most cases occur in the summer and autumn.<br/><br/>Most infected individuals are asymptomatic. Those who do develop symptoms have fever, headache, myalgia, arthralgia, nausea, vomiting, and a transient rash. Less than 1% develop meningitis/encephalitis symptoms similar to other causes of aseptic meningitis. Those with encephalitis in addition to fever and headache may have altered mental status and focal neurologic deficits including flaccid paralysis or movement disorders. <br/><br/>Detection of anti-WNV IgM antibodies (AB) in serum or CSF is the most common way to make the diagnosis. IgM AB usually is present within 3-8 days after onset of symptoms and persists up to 90 days. Data from <span class="Hyperlink"><a href="https://www.cdc.gov/mosquitoes/mosquito-control/professionals/ArboNET.html">ArboNET</a></span>, the national arboviral surveillance system managed by Centers for Disease Control and Prevention and state health departments, reveal that from 1999 to 2022 there were 56,575 cases of WNV including 28,684 cases of neuroinvasive disease. In 2023 there were 2,406 and 1,599 cases, respectively. Those historic totals for WNV are 10 times greater than the totals for all the other etiologies of neuroinvasive arboviral diseases in the US combined (Jamestown Canyon, LaCrosse, St. Louis, and Eastern Equine encephalitis n = 1813). <br/><br/>Remember to include WNV in your differential of a febrile patient with neurologic symptoms, mosquito bites, blood transfusions, and organ transplantation. Treatment is supportive care. </p> <p>The US began screening all blood donations for WNV in 2003. Organ donor screening is not universal. </p> <h2>Dengue</h2> <p>Dengue, another arbovirus, is transmitted by bites of infected <em>Aedes aegypti</em> and <em>Aedes albopictus</em> mosquitoes, which prefer to feed during the daytime. There are four dengue virus serotypes: DENV-1 DENV-2, DENV-3 and DENV-4. In endemic areas, all four serotypes are usually co-circulating and people can be infected by each one. [[{"fid":"290230","view_mode":"medstat_image_flush_right","fields":{"format":"medstat_image_flush_right","field_file_image_alt_text[und][0][value]":"Aedes aegypti mosquito","field_file_image_credit[und][0][value]":"Wikimedia Commons/Muhammad Mahdi Karim/Creative Commons License","field_file_image_caption[und][0][value]":""},"type":"media","attributes":{"class":"media-element file-medstat_image_flush_right"}}]]Long-term immunity is type specific. Heterologous protection lasts only a few months. Dengue is endemic throughout the tropics and subtropics of Asia, Africa, and the Americas. Approximately 53% of the world’s population live in an area where dengue transmission can occur. In the US, most cases are reported from Puerto Rico. Dengue is endemic in the following US territories: Puerto Rico, US Virgin Islands, American Samoa, and free associated states. Most cases reported on the mainland are travel related. However, locally acquired dengue has been reported. From 2010 to 2023 Hawaii reported 250 cases, Florida 438, and Texas 40 locally acquired cases. During that same period, Puerto Rico reported more than 32,000 cases. It is the leading cause of febrile illness for travelers returning from the Caribbean, Latin America, and South Asia.<sup> </sup>Peru is currently experiencing an outbreak with more than 25,000 cases reported since January 2024. Most cases of dengue occur in adolescents and young adults. Severe disease occurs most often in infants, those with underlying chronic disease, pregnant women, and persons infected with dengue for the second time.</p> <p>Symptoms range from a mild febrile illness to severe disease associated with hemorrhage and shock. Onset is usually 7-10 days after infection and symptoms include high fever, severe headache, retro-orbital pain, arthralgia and myalgias, nausea, and vomiting; some may develop a generalized rash. <br/><br/>The World Health Organization (WHO) classifies dengue as 1) dengue with or without warning signs for progression of disease and 2) severe dengue. Warning signs for disease progression include abdominal pain or tenderness, persistent vomiting, fluid accumulation (e.g., ascites, pericardial or pleural effusion), mucosal bleeding, restlessness, postural hypotension, liver enlargement greater than 2 cm. Severe dengue is defined as any sign of severe plasma leakage leading to shock, severe bleeding or organ failure, or fluid accumulation with respiratory distress. Management is supportive care. <br/><br/>[[{"fid":"279357","view_mode":"medstat_image_flush_right","fields":{"format":"medstat_image_flush_right","field_file_image_alt_text[und][0][value]":"Dr. Bonnie M. Word, a pediatric infectious disease specialist and director of the Houston Travel Medicine Clinic","field_file_image_credit[und][0][value]":"","field_file_image_caption[und][0][value]":"Dr. Bonnie M. Word"},"type":"media","attributes":{"class":"media-element file-medstat_image_flush_right"}}]]Prevention: In the US, Dengvaxia, a live attenuated tetravalent vaccine, is approved for use in children aged 9–16 years with laboratory-confirmed previous dengue virus infection and living in areas where dengue is endemic. It is administered at 0, 6, and 12 months. It is not available for purchase on the mainland. Continued control of the vector and personal protection is necessary to prevent recurrent infections.<sup> </sup> <br/><br/></p> <h2>CHIKV</h2> <p>Chikungunya (CHIKV), which means “that which bends up” in the Mkonde language of Tanzania, refers to the appearance of the person with severe usually symmetric arthralgias characteristic for this infection that otherwise is often clinically confused with dengue and Zika. It too is transmitted by <em>A. aegypti</em> and <em>A. albopictus</em> and is prevalent in tropical Africa, Asia, Central and South America, and the Caribbean. Like dengue it is predominantly an urban disease. The WHO reported the first case in the Western Hemisphere in Saint Martin in December 2013. By August 2014, 31 additional territories and Caribbean or South American countries reported 576,535 suspected cases.<sup> </sup>Florida first reported locally acquired CHIKV in June 2014. By December an additional 11 cases had been identified. Texas reported one case in 2015. Diagnosis is with IgM ab or PCR. Treatment is supportive with most recovering from acute illness within 2 weeks. Data in adults indicate 40-52% may develop chronic or recurrent joint pain. </p> <p>Prevention: IXCHIQ, a live attenuated vaccine, was licensed in November 2023 and recommended by the CDC in February 2024 for use in persons at least 18 years of age with travel to destinations where there is a CHIKV outbreak. It may be considered for persons traveling to a country or territory without an outbreak but with evidence of CHIKV transmission among humans within the last 5 years and those staying in endemic areas for a cumulative period of at least 6 months over a 2-year period. Specific recommendations for lab workers and persons older than 65 years were also made. This is good news for your older patients who may be participating in mission trips, volunteering, studying abroad, or just vacationing in an endemic area. Adolescent vaccine trials are ongoing and pediatric trials will soon be initiated. In addition, vector control and use of personal protective measures cannot be emphasized enough. <br/><br/>There are several other mosquito borne diseases, however our discussion here is limited to three. Why these three? WNV as a reminder that it is the most common neuroinvasive agent in the US. Dengue and CHIKV because they are not endemic in the US so they might not routinely be considered in febrile patients; both diseases have been reported and acquired on the mainland and your patients may travel to an endemic area and return home with an unwanted souvenir. You will be ready for them. <br/><br/></p> <p> <em>Dr. Word is a pediatric infectious disease specialist and director of the Houston Travel Medicine Clinic. She said she had no relevant financial disclosures. </em> </p> <h2>Suggested Reading</h2> <p>Chikungunya. Centers for Disease Control and Prevention. 2024. <span class="Hyperlink"><a href="https://www.cdc.gov/vaccines/acip/recommendations.html">https://www.cdc.gov/vaccines/acip/recommendations.html</a>.<br/><br/></span>Fagrem AC et al. <span class="Hyperlink"><a href="https://www.cdc.gov/mmwr/volumes/72/wr/mm7234a1.htm">West Nile and Other Nationally Notifiable Arboviral Diseases</a></span>–United States, 2021. MMWR Morb Mortal Wkly Rep. 2023 Aug 25;72(34):901-906. <br/><br/>Fever in Returned Travelers, <em>Travel Medicine</em> (Fourth Edition). 2019. <span class="Hyperlink"><a href="https://doi.org/10.1016/B978-0-323-54696-6.00056-2">doi: 10.1016/B978-0-323-54696-6.00056-2</a>.<br/><br/></span>Paz-Baily et al. <span class="Hyperlink"><a href="https://www.cdc.gov/mmwr/volumes/70/rr/rr7006a1.htm">Dengue Vaccine</a></span>: Recommendations of the Advisory Committee on Immunization Practices, United States, 2021 MMWR Recomm Rep. 2021 Dec 17;70(6):1-16).<br/><br/>Staples JE and Fischer M. <span class="Hyperlink"><a href="https://pubmed.ncbi.nlm.nih.gov/25184860/">Chikungunya virus in the Americas</a></span> — what a vectorborne pathogen can do. N Engl J Med. 2014 Sep 4;371(10):887-9. <br/><br/><span class="Hyperlink"><a href="https://www.cdc.gov/mosquitoes/about/diseases.html">Mosquitoes and Diseases A-Z</a></span>, Centers for Disease Control and Prevention. <span class="Hyperlink">https://www.cdc.gov/mosquitoes/about/diseases.html.</span></p> </itemContent> </newsItem> <newsItem> <itemMeta> <itemRole>teaser</itemRole> <itemClass>text</itemClass> <title/> <deck/> </itemMeta> <itemContent> </itemContent> </newsItem> </itemSet></root>
