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Recently I was in Wyoming. As I rode down the Snake River, the guide pointed out tree trunks that had been chewed on by beavers. Days later I joined a local friend for a hike to Taggart Lake. Upon reaching the end of the trail as I began to cast my eyes on the magnificent scenery, I could not help but notice several children, including toddlers, playing in the fresh warm water. The next thing out of my friend’s mouth was “You know there is Giardia in there.” Little did she know, she and the guide had just helped me select a topic for ID Consult.
Giardia, aka ”beaver fever,” was discussed in detail in this column as part of the differential of a diarrheal illness by Christopher J. Harrison, MD. However, it is the perfect time of year to revisit other recreational water–associated illnesses.
Infections acquired during recreational water activity can lead to illnesses involving the gastrointestinal tract, central nervous system, respiratory tract, skin, eyes, and ears. Pathogens, chemicals, and toxins are transmitted by ingestion, contact with contaminated water or a sick individual or animal, and inhalation of aerosols. The National Waterborne Disease and Outbreak Surveillance System (WBDOSS) collects data on waterborne disease and outbreaks associated with recreational water, drinking water, and environmental and undetermined exposures to water. All reporting to the Centers for Disease Control and Prevention (CDC) is voluntary. However, mandatory pathogen reporting requirements can vary by state. Ideally, once an agency has completed the outbreak investigation, the definitive cause and source will be determined, and interventions to prevent future outbreaks implemented.
Treated Versus Untreated Water
One useful way to help narrow the etiology of a patient’s symptoms is to consider those illnesses associated with treated water venues (e.g., pools, hot tubs, water parks) versus untreated water venues (e.g., rivers, lakes, oceans). Parents may forget to offer that information since they may not perceive a connection between water exposure and the illness, especially if they traveled within the US.
In 2021, the CDC reported results of data submitted between 2015 and 2019 from treated recreational water facilities. Of the 208 outbreaks, most (96%) were associated with public pools, hot tubs, or water playgrounds. These outbreaks resulted in at least 3,646 cases of illness, 286 hospitalizations, and 13 deaths. Overall infectious etiologies were the primary cause of illness. Of the 155 outbreaks with a confirmed etiology, Cryptosporidium was the causative pathogen in 49% of the outbreaks and accounted for 84% (2,492) of cases, while Legionella caused 42% of outbreaks, accounted for 13% (354) of cases, and was responsible for all 13 deaths. Slightly more than half (107 of 208) of the outbreaks started between June-August with Cryptosporidium accounting for 63 of the outbreaks during that period. A little more than one-third were associated with a hotel or resort. The majority of hotel recreational water–associated illnesses was associated with hot tubs. Of the 53 outbreaks without a confirmed etiology, 20 were suspected to have a chemical related etiology (excess chlorine, altered pool chemistry).
In contrast, there were 140 untreated recreational water outbreaks reported between 2000 and 2014 from 35 states and Guam involving 4,958 cases and 2 deaths. The etiology was confirmed for 103 (74%) outbreaks including 5 that had multiple etiologies and 8 due to toxins or chemicals; 7 of 8 toxins were from harmful algal blooms. Enteric pathogens were the etiology in 84% of outbreaks including: Norovirus (n = 1459), Shigella (n = 362) Avian schistosomes (n = 345), Cryptosporidium (n = 314) and Escherichia coli (n = 155).There were 24 cases of Giardia. The two deaths were due to Naegleria fowleri. The top 2 settings for these outbreaks were public parks (36%) and beaches (32%) with most outbreaks (n = 117) being associated with a lake /pond venue. Most outbreaks began between June and August.
The major differences between the two types of recreational water–associated illnesses are their most common settings and etiologies. With that in mind, let us briefly review the most common etiology from each venue.
Treated Water Venue: Cryptosporidiosis
Cryptosporidium is an oocyst-forming protozoa that causes a self-limited watery, nonbloody diarrhea which usually resolves within 10-14 days. Most patients have associated abdominal cramps, fever, and vomiting although infected persons can be asymptomatic. Infection in the immunocompromised potentially can lead to profuse and prolonged diarrhea. Oocysts are excreted in the feces of infected hosts and as little as 10 can cause infection. They can survive extreme environmental conditions in water and soil for several months and even survive up to 7 days in a properly chlorinated pool. Transmission occurs between humans via contaminated food and water or from infected animals. Oocysts have been isolated in raw or unpasteurized milk and apple cider. Incidence is highest in children 1 through 4 years of age.
Diagnosis today is usually via molecular methods (nucleic acid amplification tests, aka NAATs), due to their high sensitivity and specificity and is the preferred method. These tests can identify multiple gastrointestinal tract pathogens with a single assay. Diagnosis by microscopy or fecal immunoassay antigens are still available. Treatment is supportive in most cases. If needed, a 3-day course of nitazoxanide can be prescribed. Immunocompromised patients should be managed in consultation with an infectious disease specialist.
Untreated Water Venue: Norovirus
Norovirus is a viral illness characterized by the abrupt onset of vomiting and/or watery diarrhea, usually associated with nausea and abdominal cramps. Symptoms persist 24-72 hours, however they may be prolonged in the immunocompromised and persons at the extremes of the age spectrum. Norovirus has replaced rotavirus as the major cause of medically attended gastroenteritis. While a major cause of recreational water–associated illnesses, high attack rates also occur in semi closed communities including cruise ships, childcare centers, and schools. Transmission is fecal-oral, vomitus oral, person to person, by ingestion of contaminated food and water or touching contaminated surfaces with subsequent touching of the mouth. Asymptomatic viral shedding may occur, especially in children. Prolonged shedding (> 6 mos.) has been reported in immunocompromised hosts.
Molecular diagnosis with stool is utilized most often. Treatment is supportive.
Take Home Message
When evaluating your patients for an acute gastrointestinal illness, consider water-related activities and their potential for being the source. Encourage patients not to ignore posted advisories on beaches, to not swim if they have diarrhea, not to swallow the water they swim in and to minimize water entering their nose while swimming in warm freshwater. If you start seeing several patients with similar symptoms and/or etiology, consider contacting your local or state health department. It could be the beginning of an outbreak.
Dr. Word is a pediatric infectious disease specialist and director of the Houston Travel Medicine Clinic. She has no relevant financial disclosures.
Suggested Readings
Graciaa DS et al. Outbreaks Associated with Untreated Recreational Water — United States, 2000–2014. MMWR Morb Mortal Wkly Rep. 2018 Jun 29;67(25):701-706. doi: 10.15585/mmwr.mm6725a1.
Hlavsa MC et al. Outbreaks Associated with Treated Recreational Water — United States, 2015–2019. MMWR Morb Mortal Wkly Rep. 2021;70:733–738. doi: 10.15585/mmwr.mm7020a1.
Kimberlin DW et al., eds. Red Book Report of the Committee on Infectious Diseases. 33rd ed. American Academy of Pediatrics. 2024. Cryptosporidiosis, p 338-40 and Norovirus, p 622-624.Waterborne Outbreaks Summary Reports. CDC. 2024 April 18.
Recently I was in Wyoming. As I rode down the Snake River, the guide pointed out tree trunks that had been chewed on by beavers. Days later I joined a local friend for a hike to Taggart Lake. Upon reaching the end of the trail as I began to cast my eyes on the magnificent scenery, I could not help but notice several children, including toddlers, playing in the fresh warm water. The next thing out of my friend’s mouth was “You know there is Giardia in there.” Little did she know, she and the guide had just helped me select a topic for ID Consult.
Giardia, aka ”beaver fever,” was discussed in detail in this column as part of the differential of a diarrheal illness by Christopher J. Harrison, MD. However, it is the perfect time of year to revisit other recreational water–associated illnesses.
Infections acquired during recreational water activity can lead to illnesses involving the gastrointestinal tract, central nervous system, respiratory tract, skin, eyes, and ears. Pathogens, chemicals, and toxins are transmitted by ingestion, contact with contaminated water or a sick individual or animal, and inhalation of aerosols. The National Waterborne Disease and Outbreak Surveillance System (WBDOSS) collects data on waterborne disease and outbreaks associated with recreational water, drinking water, and environmental and undetermined exposures to water. All reporting to the Centers for Disease Control and Prevention (CDC) is voluntary. However, mandatory pathogen reporting requirements can vary by state. Ideally, once an agency has completed the outbreak investigation, the definitive cause and source will be determined, and interventions to prevent future outbreaks implemented.
Treated Versus Untreated Water
One useful way to help narrow the etiology of a patient’s symptoms is to consider those illnesses associated with treated water venues (e.g., pools, hot tubs, water parks) versus untreated water venues (e.g., rivers, lakes, oceans). Parents may forget to offer that information since they may not perceive a connection between water exposure and the illness, especially if they traveled within the US.
In 2021, the CDC reported results of data submitted between 2015 and 2019 from treated recreational water facilities. Of the 208 outbreaks, most (96%) were associated with public pools, hot tubs, or water playgrounds. These outbreaks resulted in at least 3,646 cases of illness, 286 hospitalizations, and 13 deaths. Overall infectious etiologies were the primary cause of illness. Of the 155 outbreaks with a confirmed etiology, Cryptosporidium was the causative pathogen in 49% of the outbreaks and accounted for 84% (2,492) of cases, while Legionella caused 42% of outbreaks, accounted for 13% (354) of cases, and was responsible for all 13 deaths. Slightly more than half (107 of 208) of the outbreaks started between June-August with Cryptosporidium accounting for 63 of the outbreaks during that period. A little more than one-third were associated with a hotel or resort. The majority of hotel recreational water–associated illnesses was associated with hot tubs. Of the 53 outbreaks without a confirmed etiology, 20 were suspected to have a chemical related etiology (excess chlorine, altered pool chemistry).
In contrast, there were 140 untreated recreational water outbreaks reported between 2000 and 2014 from 35 states and Guam involving 4,958 cases and 2 deaths. The etiology was confirmed for 103 (74%) outbreaks including 5 that had multiple etiologies and 8 due to toxins or chemicals; 7 of 8 toxins were from harmful algal blooms. Enteric pathogens were the etiology in 84% of outbreaks including: Norovirus (n = 1459), Shigella (n = 362) Avian schistosomes (n = 345), Cryptosporidium (n = 314) and Escherichia coli (n = 155).There were 24 cases of Giardia. The two deaths were due to Naegleria fowleri. The top 2 settings for these outbreaks were public parks (36%) and beaches (32%) with most outbreaks (n = 117) being associated with a lake /pond venue. Most outbreaks began between June and August.
The major differences between the two types of recreational water–associated illnesses are their most common settings and etiologies. With that in mind, let us briefly review the most common etiology from each venue.
Treated Water Venue: Cryptosporidiosis
Cryptosporidium is an oocyst-forming protozoa that causes a self-limited watery, nonbloody diarrhea which usually resolves within 10-14 days. Most patients have associated abdominal cramps, fever, and vomiting although infected persons can be asymptomatic. Infection in the immunocompromised potentially can lead to profuse and prolonged diarrhea. Oocysts are excreted in the feces of infected hosts and as little as 10 can cause infection. They can survive extreme environmental conditions in water and soil for several months and even survive up to 7 days in a properly chlorinated pool. Transmission occurs between humans via contaminated food and water or from infected animals. Oocysts have been isolated in raw or unpasteurized milk and apple cider. Incidence is highest in children 1 through 4 years of age.
Diagnosis today is usually via molecular methods (nucleic acid amplification tests, aka NAATs), due to their high sensitivity and specificity and is the preferred method. These tests can identify multiple gastrointestinal tract pathogens with a single assay. Diagnosis by microscopy or fecal immunoassay antigens are still available. Treatment is supportive in most cases. If needed, a 3-day course of nitazoxanide can be prescribed. Immunocompromised patients should be managed in consultation with an infectious disease specialist.
Untreated Water Venue: Norovirus
Norovirus is a viral illness characterized by the abrupt onset of vomiting and/or watery diarrhea, usually associated with nausea and abdominal cramps. Symptoms persist 24-72 hours, however they may be prolonged in the immunocompromised and persons at the extremes of the age spectrum. Norovirus has replaced rotavirus as the major cause of medically attended gastroenteritis. While a major cause of recreational water–associated illnesses, high attack rates also occur in semi closed communities including cruise ships, childcare centers, and schools. Transmission is fecal-oral, vomitus oral, person to person, by ingestion of contaminated food and water or touching contaminated surfaces with subsequent touching of the mouth. Asymptomatic viral shedding may occur, especially in children. Prolonged shedding (> 6 mos.) has been reported in immunocompromised hosts.
Molecular diagnosis with stool is utilized most often. Treatment is supportive.
Take Home Message
When evaluating your patients for an acute gastrointestinal illness, consider water-related activities and their potential for being the source. Encourage patients not to ignore posted advisories on beaches, to not swim if they have diarrhea, not to swallow the water they swim in and to minimize water entering their nose while swimming in warm freshwater. If you start seeing several patients with similar symptoms and/or etiology, consider contacting your local or state health department. It could be the beginning of an outbreak.
Dr. Word is a pediatric infectious disease specialist and director of the Houston Travel Medicine Clinic. She has no relevant financial disclosures.
Suggested Readings
Graciaa DS et al. Outbreaks Associated with Untreated Recreational Water — United States, 2000–2014. MMWR Morb Mortal Wkly Rep. 2018 Jun 29;67(25):701-706. doi: 10.15585/mmwr.mm6725a1.
Hlavsa MC et al. Outbreaks Associated with Treated Recreational Water — United States, 2015–2019. MMWR Morb Mortal Wkly Rep. 2021;70:733–738. doi: 10.15585/mmwr.mm7020a1.
Kimberlin DW et al., eds. Red Book Report of the Committee on Infectious Diseases. 33rd ed. American Academy of Pediatrics. 2024. Cryptosporidiosis, p 338-40 and Norovirus, p 622-624.Waterborne Outbreaks Summary Reports. CDC. 2024 April 18.
Recently I was in Wyoming. As I rode down the Snake River, the guide pointed out tree trunks that had been chewed on by beavers. Days later I joined a local friend for a hike to Taggart Lake. Upon reaching the end of the trail as I began to cast my eyes on the magnificent scenery, I could not help but notice several children, including toddlers, playing in the fresh warm water. The next thing out of my friend’s mouth was “You know there is Giardia in there.” Little did she know, she and the guide had just helped me select a topic for ID Consult.
Giardia, aka ”beaver fever,” was discussed in detail in this column as part of the differential of a diarrheal illness by Christopher J. Harrison, MD. However, it is the perfect time of year to revisit other recreational water–associated illnesses.
Infections acquired during recreational water activity can lead to illnesses involving the gastrointestinal tract, central nervous system, respiratory tract, skin, eyes, and ears. Pathogens, chemicals, and toxins are transmitted by ingestion, contact with contaminated water or a sick individual or animal, and inhalation of aerosols. The National Waterborne Disease and Outbreak Surveillance System (WBDOSS) collects data on waterborne disease and outbreaks associated with recreational water, drinking water, and environmental and undetermined exposures to water. All reporting to the Centers for Disease Control and Prevention (CDC) is voluntary. However, mandatory pathogen reporting requirements can vary by state. Ideally, once an agency has completed the outbreak investigation, the definitive cause and source will be determined, and interventions to prevent future outbreaks implemented.
Treated Versus Untreated Water
One useful way to help narrow the etiology of a patient’s symptoms is to consider those illnesses associated with treated water venues (e.g., pools, hot tubs, water parks) versus untreated water venues (e.g., rivers, lakes, oceans). Parents may forget to offer that information since they may not perceive a connection between water exposure and the illness, especially if they traveled within the US.
In 2021, the CDC reported results of data submitted between 2015 and 2019 from treated recreational water facilities. Of the 208 outbreaks, most (96%) were associated with public pools, hot tubs, or water playgrounds. These outbreaks resulted in at least 3,646 cases of illness, 286 hospitalizations, and 13 deaths. Overall infectious etiologies were the primary cause of illness. Of the 155 outbreaks with a confirmed etiology, Cryptosporidium was the causative pathogen in 49% of the outbreaks and accounted for 84% (2,492) of cases, while Legionella caused 42% of outbreaks, accounted for 13% (354) of cases, and was responsible for all 13 deaths. Slightly more than half (107 of 208) of the outbreaks started between June-August with Cryptosporidium accounting for 63 of the outbreaks during that period. A little more than one-third were associated with a hotel or resort. The majority of hotel recreational water–associated illnesses was associated with hot tubs. Of the 53 outbreaks without a confirmed etiology, 20 were suspected to have a chemical related etiology (excess chlorine, altered pool chemistry).
In contrast, there were 140 untreated recreational water outbreaks reported between 2000 and 2014 from 35 states and Guam involving 4,958 cases and 2 deaths. The etiology was confirmed for 103 (74%) outbreaks including 5 that had multiple etiologies and 8 due to toxins or chemicals; 7 of 8 toxins were from harmful algal blooms. Enteric pathogens were the etiology in 84% of outbreaks including: Norovirus (n = 1459), Shigella (n = 362) Avian schistosomes (n = 345), Cryptosporidium (n = 314) and Escherichia coli (n = 155).There were 24 cases of Giardia. The two deaths were due to Naegleria fowleri. The top 2 settings for these outbreaks were public parks (36%) and beaches (32%) with most outbreaks (n = 117) being associated with a lake /pond venue. Most outbreaks began between June and August.
The major differences between the two types of recreational water–associated illnesses are their most common settings and etiologies. With that in mind, let us briefly review the most common etiology from each venue.
Treated Water Venue: Cryptosporidiosis
Cryptosporidium is an oocyst-forming protozoa that causes a self-limited watery, nonbloody diarrhea which usually resolves within 10-14 days. Most patients have associated abdominal cramps, fever, and vomiting although infected persons can be asymptomatic. Infection in the immunocompromised potentially can lead to profuse and prolonged diarrhea. Oocysts are excreted in the feces of infected hosts and as little as 10 can cause infection. They can survive extreme environmental conditions in water and soil for several months and even survive up to 7 days in a properly chlorinated pool. Transmission occurs between humans via contaminated food and water or from infected animals. Oocysts have been isolated in raw or unpasteurized milk and apple cider. Incidence is highest in children 1 through 4 years of age.
Diagnosis today is usually via molecular methods (nucleic acid amplification tests, aka NAATs), due to their high sensitivity and specificity and is the preferred method. These tests can identify multiple gastrointestinal tract pathogens with a single assay. Diagnosis by microscopy or fecal immunoassay antigens are still available. Treatment is supportive in most cases. If needed, a 3-day course of nitazoxanide can be prescribed. Immunocompromised patients should be managed in consultation with an infectious disease specialist.
Untreated Water Venue: Norovirus
Norovirus is a viral illness characterized by the abrupt onset of vomiting and/or watery diarrhea, usually associated with nausea and abdominal cramps. Symptoms persist 24-72 hours, however they may be prolonged in the immunocompromised and persons at the extremes of the age spectrum. Norovirus has replaced rotavirus as the major cause of medically attended gastroenteritis. While a major cause of recreational water–associated illnesses, high attack rates also occur in semi closed communities including cruise ships, childcare centers, and schools. Transmission is fecal-oral, vomitus oral, person to person, by ingestion of contaminated food and water or touching contaminated surfaces with subsequent touching of the mouth. Asymptomatic viral shedding may occur, especially in children. Prolonged shedding (> 6 mos.) has been reported in immunocompromised hosts.
Molecular diagnosis with stool is utilized most often. Treatment is supportive.
Take Home Message
When evaluating your patients for an acute gastrointestinal illness, consider water-related activities and their potential for being the source. Encourage patients not to ignore posted advisories on beaches, to not swim if they have diarrhea, not to swallow the water they swim in and to minimize water entering their nose while swimming in warm freshwater. If you start seeing several patients with similar symptoms and/or etiology, consider contacting your local or state health department. It could be the beginning of an outbreak.
Dr. Word is a pediatric infectious disease specialist and director of the Houston Travel Medicine Clinic. She has no relevant financial disclosures.
Suggested Readings
Graciaa DS et al. Outbreaks Associated with Untreated Recreational Water — United States, 2000–2014. MMWR Morb Mortal Wkly Rep. 2018 Jun 29;67(25):701-706. doi: 10.15585/mmwr.mm6725a1.
Hlavsa MC et al. Outbreaks Associated with Treated Recreational Water — United States, 2015–2019. MMWR Morb Mortal Wkly Rep. 2021;70:733–738. doi: 10.15585/mmwr.mm7020a1.
Kimberlin DW et al., eds. Red Book Report of the Committee on Infectious Diseases. 33rd ed. American Academy of Pediatrics. 2024. Cryptosporidiosis, p 338-40 and Norovirus, p 622-624.Waterborne Outbreaks Summary Reports. CDC. 2024 April 18.