“Experts at the London School of Hygiene & Tropical Medicine (LSHTM) have explained how the spread of the virus differs to those that commonly spread between humans, such as flu (influenza) or COVID-19.
Below, Professor Michael Marks, NIHR Research Professor at LSHTM and Honorary Consultant in Infectious Diseases at the Hospital for Tropical Diseases at University College London Hospital, helps answer common questions around the hantavirus outbreak.
What is hantavirus and how does it spread?
Hantaviruses are a group of viruses carried by rodents, such as mice and rats. Rodents infected with hantavirus do not usually show signs of illness. People usually become infected by breathing in air contaminated with virus particles from rodent urine, droppings or saliva.
Most hantaviruses do not spread between humans. One strain, called the Andes hantavirus, can spread from person-to-person but this is extremely rare as it requires very close contact. It does not spread easily like other viruses known to infect humans, such as flu or COVID-19.
Professor Marks said: “Hantaviruses are actually a family of viruses. The primary mode of transmission of all of these viruses is through exposure to secretions (saliva, urine, faeces) of specific species of rats. The rats are normally well. People inhale these secretions which results in the virus getting into the lungs and blood stream.
“This specific outbreak has been identified as being caused by Andes virus which is one of the causes of Hantavirus cardio-pulmonary syndrome. This is the only hantavirus currently known to have described cases of human-to-human transmission. Even for Andes virus this is rare – i.e. most cases are still caused by exposure to rats and their secretions.”
Where is hantavirus usually found?
Different strains of hantavirus can be found in some areas of Europe, Africa and Asia. The Andes strain, which is responsible for the current outbreak, is usually found in rural parts of South America.
Rodents in the UK do not carry Andes hantavirus. Only Seoul hantavirus, which does not transmit from person to person, has ever been identified in the UK.
What are the symptoms of hantavirus and how is it treated?
According to the UK Health Security Agency (UKHSA), symptoms of hantavirus infection can include fever, extreme fatigue, muscle aches, stomach pain, nausea, vomiting, diarrhoea or shortness of breath. Symptoms usually appear between two to four weeks after being exposed to the virus.
There is currently no specific treatment or vaccine, but hospitals are trained to help care for those who become unwell.
Is there a wider risk to the UK or other countries from this outbreak?
Although hantavirus is a serious infection and can be fatal without prompt treatment, the risk to the wider UK population is very low.
Hantavirus does not spread easily through everyday social contact like walking in public spaces, shops, workplaces or schools. It requires prolonged close contact with a person who is visibly unwell.
Professor Marks said: “In the current outbreak it is likely that the initial cases were indeed caused by exposure to rats. Then it seems plausible that in the context of a cruise ship – where people are in very close proximity – that there has been some onward transmission to other individuals. Human to human transmission is likely due to prolonged and close exposure to someone who is very unwell with a high level of virus in their respiratory secretions.
“The incubation period for Hantaviruses can be quite long (several weeks). As noted above, in the rare cases where human to human transmission has occurred this is in the context of people who are unwell and who have sustained close contact with other people. These individuals from the ship are well – we do not even know they have Hantavirus infection, only that they have plausibly been exposed.”