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The hantavirus found in Sweden is the Puumala virus, which causes nephropathia epidemica (bank vole fever). Professor Clas Ahlm’s research focuses on studying the disease mechanisms of nephropathia epidemica, as well as immune responses during acute infection and long-term immunity.

ImageHans Karlsson

Is this an outbreak that people in Sweden need to worry about? We put our questions to Professor Clas Ahlm, senior consultant and professor of infectious diseases at the Department of Clinical Microbiology at Umeå University, who studies the hantavirus variant found in Sweden.

What is currently known about the hantavirus outbreak on the cruise ship *MV Hondius*?

“The outbreak on board the *MV Hondius* cruise ship has been caused by Andes virus, a rarer and more aggressive type of hantavirus found in South America. The virus is spread via rodents and can cause severe illness with serious lung involvement and a high mortality rate, even with advanced hospital care.”

How does this virus differ from the hantaviruses found in Sweden?

“Unlike the hantaviruses found in Sweden – primarily Puumala virus, which causes nephropathia epidemica (bank vole fever) – Andes virus can, in rare cases, be transmitted between humans, usually through close contact. This feature makes the outbreak more serious, although its transmissibility is still significantly lower than that of well-known airborne viruses such as influenza and coronaviruses.”

How is hantavirus transmitted, and how common is human-to-human transmission?

“To our knowledge, only the type of hantavirus found in South America, Andes virus, can be transmitted between humans. Close or prolonged contact is required for such transmission.”

Is there a risk that this variant could reach Sweden, for example through travel?

“Yes, the virus has a relatively long incubation period, around two weeks and in some cases up to six to eight weeks. This means that infected individuals may travel to other regions or countries, potentially leading to secondary cases, where the infected person transmits the virus to others. However, the risk of further spread is considered low if exposed individuals take appropriate precautions.”

What symptoms does hantavirus cause, and is there reason for concern?

“The symptoms of hantavirus infection are flu-like, including fever, general malaise, and often body aches and headaches. Depending on the type of hantavirus, either the lungs or the kidneys are primarily affected. Currently, there is no vaccine and no specific treatment for hantavirus infection.

“There is no reason for concern among the general public. However, this event highlights the importance of strong preparedness within both society and the healthcare system to rapidly detect and manage unusual infectious disease outbreaks.”

Tell us about the hantavirus research underway at Umeå University!

“At Umeå University, several research projects are ongoing, focusing on hantaviruses, including studies of disease mechanisms, immune responses during acute infection and immunity, as well as ecological aspects. Researchers at Umeå University are also involved in international collaborations aimed at developing vaccines and future treatments.

“My research focuses on the disease mechanisms of nephropathia epidemica, immune responses during acute illness, and long-term immunity. We aim to answer questions such as: What happens in the body during infection? How can we treat the disease, alleviate its course, and prevent severe illness and death? Does infection confer lifelong immunity, and can we develop vaccines that protect against hantavirus infection?”