Overview
Health authorities are investigating an outbreak of hantavirus on a luxury cruise ship that has resulted in three fatalities and a further five confirmed or suspected cases. The World Health Organization has identified the agent involved as the Andes strain of hantavirus. Experts from the WHO and several countries are examining the situation aboard the vessel and tracing contacts to limit additional spread.
What hantavirus is
Hantaviruses are a group of viruses carried by rodents that can infect humans and cause a range of illnesses. According to WHO estimates, there are between 10,000 and 100,000 human cases globally each year, with clinical severity differing by strain.
Pathways of transmission
The primary route of hantavirus transmission to people is through contact with infected rodents - typically rats or mice - or exposure to their urine, droppings or saliva. The virus can become airborne when contaminated material is disturbed, for example during cleaning of infested spaces, allowing inhalation of viral particles. Transmission via contaminated surfaces is less common.
Of note, the Andes strain of hantavirus, which is largely found in Argentina and Chile, is the only hantavirus variant known to spread between humans through close, prolonged contact. The WHO confirmed that the cruise ship outbreak involves the Andes strain.
Typical symptoms and clinical course
Signs of hantavirus infection generally appear between one and eight weeks after exposure. Common early symptoms may include fever, muscle aches and gastrointestinal complaints. Different hantaviruses produce different clinical syndromes in different regions.
- In Europe and Asia, hantaviruses have been associated with haemorrhagic fever with renal syndrome, which primarily affects the kidneys and the circulatory system.
- In the Americas, infections can lead to hantavirus cardiopulmonary syndrome, a rapidly progressing illness characterized by fluid accumulation in the lungs and cardiac complications. The WHO reports case fatality rates for hantavirus cardiopulmonary syndrome can reach up to 50 percent, compared with a 1-15 percent range for the infections more common in Asia and Europe.
Treatment and prevention
There is no specific antiviral treatment approved for hantavirus infection. Medical care is therefore supportive, focused on rest, fluid management and, when necessary, respiratory support such as mechanical ventilation. Preventive measures emphasize limiting contact with rodents by maintaining clean surroundings and reducing opportunities for rodent infestation.
During outbreaks, contact tracing is used to identify people who may have been exposed and to provide earlier access to hospital care, which can improve individual outcomes and help prevent further transmission.
Public health risk and regional trends
While the cruise ship incident is unusual and the subject of an ongoing probe by WHO teams and international partners, the WHO has stated that the risk to the general public remains low. At the same time, the WHO regional office for the Americas reported in December that hantavirus infections were on the rise in the region, with particular increases noted in Bolivia and Paraguay. Brazil and Argentina have experienced rising lethality; Argentina reported 21 deaths last year among 66 confirmed cases of hantavirus pulmonary syndrome, a 32 percent fatality rate compared with an average fatality rate of 15 percent over the prior four years.
Investigations and public health responses are continuing to determine the full scope of the outbreak aboard the ship and to identify any additional exposed individuals who may require medical attention.