Swedish officials have ended investigations into an increase in domestic cryptosporidium infections because the number of cases decreased since the start of February.
The Public Health Agency of Sweden (Folkhälsomyndigheten) and Swedish Food Agency (Livsmedelsverket) helped to identify five foodborne outbreaks and other infections affecting more than 230 people.
During the autumn, a large increase in people with cryptosporidiosis infected in Sweden, was investigated. The number of reported cases was highest during two weeks in November.
Using microbiological typing results of samples from cases, two dominant types were identified, Cryptosporidium parvum subtype IIdA22G1c and IIdA24G1. People with these subtypes occurred mainly until mid-November. Both of them had been detected earlier in 2019 and in the previous year.
Spinach in a drink
During October to December, 122 cases with the subtype IIdA22G1c were recorded in 10 regions. Most were in Stockholm with 58 cases, Västra Götaland and Halland both with 16. Other regions had one to nine infections. About as many men as women became ill. Average age was 39 years and the range was between two to 83 years old.
Interviews with people infected with both types of Cryptosporidium to see what they ate or drank before they became ill revealed those with subtype IIdA22G1c were more likely to have drunk pre-purchased freshly pressed fruit and vegetable drinks compared to people with the other subtype.
An investigation indicated it was the spinach in the drink, delivered in October, that was the source of infection.
From October to December, 65 people with the subtype IIdA24G1 fell ill in 12 regions. Most were reported from Västra Götaland with 13 cases, Stockholm and Östergötland had 12 and Jönköping with 11. Other regions had one to three infections. More women (62 percent) than men (38 percent) became ill. The average age was 40 and the range was from 11 to 79 years old.
No specific food could be identified as the source of infection based on survey responses but some type of product with a short shelf life was suspected.
During December, three local outbreaks were also investigated by infection control and environmental agencies following Christmas meals.
Samples from patients showed they had two different subtypes of Cryptosporidium parvum; IIdA21G1* for two of the incidents and IIdA20G1e at the other.
In all three outbreaks, the risk of getting sick was higher if kale salad had been consumed.
Authorities traced the kale to four different growers in southern Sweden. The subtypes were also found in cases with no known connection to the Christmas meals during December, meaning it was likely the foods were also distributed to grocery stores or other restaurants.
Due to the national increase from October to December, 300 samples were analyzed. Of typed samples, 193 were part of the above-mentioned outbreaks. A further 38 cases with the same subtypes as the December outbreaks were identified but they were not directly linked to the outbreaks.
This work also identified several different Cryptosporidium parvum and Cryptosporidium hominis subtypes, as well as other cryptosporidium species.
Since the beginning of February, the number of cryptosporidiosis cases has gone down to similar levels for the same time in previous years.
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