If it’s swimming season, it’s also Cryptosporidium season. The parasite, spread through feces of infected humans or animals, is the culprit in most disease outbreaks linked to water.
Between 2009 and 2017, Crypto-related outbreaks increased an average 13% per year, according to the CDC. In the 444 outbreaks reported, 7,465 people became sick, 287 people were hospitalized, and 1 person died. The CDC says these numbers are likely to be underestimates.
One-third of the outbreaks were in treated swimming water, including pools and water playgrounds. Smaller percentages were linked to contact with cattle, infected people in childcare settings, and raw milk or apple cider.
Crypto’s tough protective shell is the secret to its long life. It can survive for days even in chlorinated pools or on surfaces disinfected with chlorine bleach. Moreover, Cryptosporidium oocysts are immediately infectious upon excretion and are excreted in numbers multiple orders of magnitude higher than the human infectious dose (≤ 10 oocysts). Just a few germs can make someone sick—and there can be millions in a pool. Infection with Cryptosporidium can cause profuse, watery diarrhea that lasts for up to 3 weeks. It’s particularly dangerous for immunocompromised patients, leading to malnutrition and wasting.
The CDC has some advice for staying Crypto free:
- Don’t swim or let kids swim if anyone has diarrhea, and keep them home from daycare;
- Don’t swallow the water you swim in;
- Wash hands with soap and water after any contact with animals, especially animal feces ( note: alcohol-based hand sanitizers are not effective against Crypto; hydrogen peroxide should be used in childcare settings to disinfect);
- Remove shoes worn in animal environments before going inside your home; and
- Drink only pasteurized milk or apple cider.
Although the numbers are still high, the CDC says testing has improved and might be helping with increased detection, especially since CryptoNet, the first US molecularly based surveillance system for a parasitic disease, was instituted. Based on DNA fingerprinting, it has already demonstrated that it can elucidate Cryptosporidium transmission chains in treated recreational water outbreaks, the CDC says, and has the potential to do the same for investigations in other Crypto outbreaks.