Cowpox virus infection in pet rat owners: not always immediately recognized.

Background: The aim of this article is to make physicians of all specialties aware of the possible variations of clinical course in human cowpox infection. This has been a matter of current interest since the detection of a first cluster of infections among owners of white pet rats in the Krefeld area in the spring of 2008. Two further cases arose in the Krefeld area in November 2008, and there have since been multiple further reports from various regions in Germany and the neighboring countries.

Method: The authors report on the first six documented cases of infection with cowpox virus among young persons owning pet rats, with both typical and atypical clinical courses.

Results: The clinical, molecular biological, and serological findings confirmed cowpox virus infection in all six cases. The DNA sequence of the cowpox virus hemagglutinin gene was identical in all patients. The infections had arisen after direct contact with pet rats.

Conclusions: Molecular genetic analysis of the cases described here suggests that the observed occurrence of cowpox virus infection among human beings and pet rats in multiple geographical areas represents a unitary epidemiological event that has not yet come under control. Further cases can be expected.