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.
Dr. Bonnie M. Word
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.