Hantaviruses (family Bunyaviridae, genus Hantavirus) are rodent-borne, zoonotic (acquired from animals), enveloped RNA viruses, and include the causative agents of haemorrhagic fever with renal syndrome (HFRS), and hantavirus pulmonary syndrome (HPS). HFRS occurs in Europe and Asia, while HPS occurs in North and South America. As for many infections, it is likely that asymptomatic or mild infections greatly outnumber characteristic symptomatic infections.
Each hantavirus is specific to a different rodent host (more information). Once infected the rodent will secrete infectious virus for prolonged periods, probably for life. Transmission of virus to human occurs through the inhalation of infected animal excreta and fluids, i.e. urine, faeces and saliva.
Haemorrhagic fever with renal syndrome (HFRS) is a group of clinically similar illnesses occurring worldwide, and including Korean haemorrhagic fever, epidemic haemorrhagic fever, and nephropathia epidemica. The viruses that cause HFRS include Hantaan, Dobrava, Seoul, and Puumala. The incubation period is generally 2-4 weeks (range 2 days to 8 weeks).
Infection with these viruses can cause a disease characterised by fever, headache, gastrointestinal symptoms and renal dysfunction. The more severe forms of disease have haemorrhagic (bleeding) manifestations. Dobrova and Hantaan viruses cause a more severe HFRS with fever, haemorrhage, and renal failure, and a mortality rate of up to 15%. Seoul virus causes a moderately severe disease resembling that due to Hantaan virus.
Nephropathia epidemica is the mildest form of HFRS, and is caused by Puumala virus, the most common hantavirus, present in most countries in north-western Europe. Nephropathia epidemica has an abrupt onset with fever and myalgias, thrombocytopaenia (low blood platelet count) and sometimes myopia. An acute renal failure occasionally requiring dialysis can occur.The mortality rate is < 0.1%.
Haantan virus is widely distributed in eastern Asia, particularly in China, Russia, and Korea. Puumala virus is found in Scandinavia, western Europe, and Russia. Dobrava virus is found primarily in the Balkans, and Seoul virus is found worldwide. Saaremaa virus also circulates in northwest Europe.
About 150,000 cases of HFRS are thought to occur annually worldwide. Very few cases of hantavirus infection have been confirmed in the United Kingdom, although there are seroprevalence data to suggest that exposure does occur.
The first case of Seoul hantavirus infection in the UK was confirmed in 2012, with virus being isolated from wild rats at the location of exposure. Jameson et al, Eurosurveillance 4 Jan 2013 [external link].
In January 2013, the first cases of Seoul hantavirus infection linked to pet rats were identified. Jameson et al. Eurosurveillance 28 February 2013 [external link].
Sin Nombre virus, the common cause of HPS in the USA, was discovered in 1993 following a cluster of acute and fatal illness in previously healthy adults. The cluster occurred in an area of the southwestern USA known as 'Four Corners'. It was later established that the virus had caused human disease at least as early as 1959, and that the disease syndrome was well-recognised among the Navajo indians in whom it was observed. By the end of 2012, a total of 617 cases of HPS had been reported in the United States. Thirty-five percent of all reported cases were fatal.
HPS is more common in South America than in North America. Cases have been identified in Argentina, Bolivia, Brazil, Chile, Ecuador, Paraguay, Panama and Uruguay and Venezuela. Andes virus causes HPS in Argentina and Chile, and is the only hantavirus known to have been transmitted from person to person. Large outbreaks have been rare and have usually been associated with human disturbance and land-use changes or with unusual environmental events such as increased rainfall.