Scientists in the United Kingdom have reported an ongoing nationwide increase in cases of cryptosporidiosis.

The rise in infections was first noted in August and is mainly due to Cryptosporidium Hominis, although there are also hundreds of Cryptosporidium parvum cases.

There have been 2,411 laboratory confirmed cases in the UK with 2,032 in England, 163 in Wales, 127 in Scotland and 89 in Northern Ireland from mid-August to early October.

Given the scale and geographical spread of patients across the UK, a single local exposure is an unlikely cause, according to the study published in the journal Eurosurveillance.

Other countries affected

In October, Irish health officials issued a warning after a rise in cryptosporidium infections in people returning from abroad. A total of 64 people had fallen sick, with 44 lab-confirmed cases. 

An increase has also been noted in Luxembourg and the Netherlands since the end of August and during September. In the Netherlands, the number of cases in September was 129, compared with an average of 72 during September for 2016 to 2019. In Luxembourg, there were 97 lab-confirmed notifications between late August and early October, compared with 21 during the same period in 2022.

The European Centre for Disease Prevention and Control (ECDC) said the rise could be due to a combination of factors related to travel and extreme climate conditions. The agency added cryptosporidiosis is under-reported in many countries, which limits the ability to accurately assess the risk.

Information from cases in England and Wales, identified foreign travel in 250 of 463 respondents and swimming in 234 of 353 cases. Other sources such as contaminated food have not been ruled out as contributing to the spike in infections. Cryptosporidium can be spread in a chlorinated pool because it is resistant to chlorine.

A standardized electronic questionnaire was used including questions on foreign travel, food and water exposures and interaction with animals.

Travel-related cases

Of the 394 cases in England who provided information on travel, 215 reported going abroad in the 14 days preceding illness, of which 96 mentioned Spain including the Spanish mainland or the Balearic Islands.

Two incidents linked to a small number of cases have been identified and are being investigated by environmental health teams in local authorities.

More than half of the 224 questionnaire respondents had an illness duration of more than 10 days while 19 reported being sick for more than 20 days.

From 475 cases, the 20 to 39 year old age group was the most affected but more than 150 patients are under the age of 10.

Survey responses have not identified common exposures or settings that may explain large numbers of cases. Cryptosporidium hominis infections normally increase at this time of year but not by so much. The rise may also reflect more summer travel to Spain and other Mediterranean countries.

The most common symptom is watery diarrhea. Some people may also experience dehydration, weight loss, stomach cramps, fever, nausea and vomiting. Others may not have symptoms at all. Symptoms usually last between 1 to 2 weeks. While it is a mild disease in healthy people, it can be worse in small children and elderly people and can be very serious for immunocompromised people. Specific tests are required because the symptoms can mimic other diseases.