Self-report. Hantavirus is found naturally in various rodents (mice, rats, and voles). In humans, Hantavirus causes hemorrhagic fever with renal syndrome and Hantavirus-associated pulmonary syndrome with variable mortality. In Europe, Puumala Hantavirus causes a milder form of hemorrhagic fever with renal syndrome called epidemic kidney fever or vole fever. However, vulture fever can have a very serious course, but the overall fatality rate is less than 1 percent.

Burrowing fever is a notifiable disease in Sweden. The diagnosis should be taken into consideration if the patient presents with high fever, abdominal, muscle, or head pain and has signs of kidney involvement, including proteinuria and hematuria. Between 100 and 450 cases of vole fever are diagnosed each year in the northern part of the country. Previous studies have shown an increased prevalence of antibodies to norbuten/fasterbuten (13.4 percent in 2016). [1].

The first case of vulture fever in the southern part of Sweden was reported in 2018. The case occurred in Skane, which is located more than 500 km south of Sweden's previously known southernmost occurrence of vulture fever. [2]. In 2020, another case of vole fever was reported in the area. To support the theory of local transmission, wood rats were captured near the first patient's residence and analyzed for the presence of hantavirus. 9 out of 74 mice carried genetic material (RNA) from Hantavirus. Phylogenetic studies showed that the virus was Puumala Hantavirus, but differed significantly from variants circulating in northern Sweden and Denmark, and was instead more closely related to Puumala Hantavirus variants from Finland and Karelia. [3].

The results raise questions about the origin of the virus and its current spread in southern Sweden. Did the Puumala Hantavirus start circulating relatively recently in Scania, and is this the explanation for the fact that so far only isolated cases of vole fever have been reported from there? How did the Hanta pumala virus spread to Scania? How does the Puumala Scanian hantavirus variant compare to previously discovered Puumala hantaviruses in terms of virulence?

The study was recently published in the scientific journal Emerging Infectious Diseases (EID), published by the US health watchdog CDC (Centers for Disease Control and Prevention), and was funded by the European Union (Horizon 2020) and Scilifelab (Pandemic Laboratory Preparedness).