By NewsDesk  @infectiousdiseasenews

Since the last report on the Cryptosporidium outbreak in Sweden about two weeks ago, health officials say the number of reported cases has decreased in recent weeks.

Cryptosporidium life cycle/CDC

While cases are declining, the number of cases reported per week remains slightly higher compared to the same period in previous years. To date, some 400 Cryptosporidium cases have been recorded.

Most cases have been reported from Stockholm, Östergötland, Västra Götaland, Halland, Jönköping and Uppsala.

The Public Health Authority analyzes samples from the cases to determine what type of cryptosporidium they have become ill from. Of the 202 samples analyzed so far, 93 have been shown to belong to subtype (A) and 58 belong to subtype B of Cryptosporidium parvum. In addition to this subtype, a number of different subtypes have been detected.

The fact that different subtypes are seen indicates that there are different sources of infection for the cases reported during the fall. From the survey studies it was shown that cases with subtype A have drunk to a greater extent pre-purchased freshly squeezed fruit and vegetable drinks that are no longer on the market when the shelf life is short. The majority (almost 80%) of cases with subtype A were reported to have fallen ill during the month of October, which indicates that the outbreak has subsided.

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The investigation of cases with subtype B continues and the affected infection protection units, municipalities, the Swedish National Food Agency and the Public Health Authority try to identify the source of the infection. As part of the investigation, those who have become ill respond to questionnaires about what they ate and drank before they became ill. The source of infection for subtype B is unknown so far but the investigation does not lead to the same source of infection as for subtype A.  (Subtype A = IIdA22G1c, subtype B = IIdA24G1)