UK Cryptosporidium cases on the rise, investigations ongoing

A recent rapid communication report by the United Kingdom Health Security Agency, UK, draws attention to the unprecedented and ongoing increase in cryptosporidiosis cases in the UK. Currently, cases are at more than double the expected rate and rising.

In a report, "Preliminary investigation of a significant national Cryptosporidium exceedance in the United Kingdom, August 2023 and ongoing," published in Eurosurvailence, Europe's journal on infectious disease surveillance, epidemiology, prevention and control, the team offers insights into the unusual surge in cases of cryptosporidiosis.

Cryptosporidiosis (also known as Crypto) is a disease caused by Cryptosporidium parasite species, primarily C. hominis and C. parvum. The most common symptom is watery diarrhea followed by an assortment of other unpleasant effects like stomach pain, nausea, vomiting, fever and the potential for weight loss and dehydration from the experience.

Infection is caused by ingesting the parasite's "eggs" or oocytes, which are deposited in a host's gut and escape via defecation. While ingesting feces seems entirely avoidable in daily life, disease outbreaks can be associated with various secondary sources, including water supplies, swimming pools, animal contact, person-to-person transmission, ingesting soil and poorly prepared food.

Surveillance data indicates that the increase in cases has been widespread across England, Wales, Scotland, and Northern Ireland. Genotyping and sequencing reveal the prevalence of an unusual (in the UK) subtype of C. hominis, which is most commonly transmitted from person to person.

Exposure data overall is diverse and lacks a clear culprit, though foreign travel, especially to Spain and other Mediterranean countries, is the most common factor among cases. Spain is historically identified as the most popular destination for UK travelers, so the association could have a confounding overlap of statistical probability.

Swimming, locally or abroad, is also associated with a higher odds ratio for exposure. If warmer destinations are the source, swimming activities at those locations could be accelerating the spread.

The authors caution that other sources, such as food supply, cannot currently be excluded from contributing to the spike in cases as survey responses have yet to identify common specific exposures or settings that explain such large numbers of cases.

Prevention precautions are the somewhat familiar drill of washing hands with soap and water, though alcohol-based hand sanitizers are not effective against Crypto. The perhaps previously under-recommended safety measure is to avoid swallowing water while swimming, especially in a public pool setting.

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