11 August 2005

Hantavirus Infections in Europe

A large increase in hantavirus infections has been detected simultaneously in Belgium, Germany and France this year [1]. Between 1 January and 15 June 2005, 120 laboratory confirmed cases were reported in Belgium, 115 cases in France and 258 cases in Germany, compared to 47, 55 and 64 cases respectively during the same time period in 2004. The increase in cases has occurred earlier in the year compared with previous years. In Belgium, the areas most affected are Luxembourg, Liège and the Namur provinces; in France the Ardennes, Aisne and Jura administrative departments; in Germany the federal states of Nordrhein-Westfalen, Niedersachsen, Hessen, Baden-Württemberg and Bayern. Further increases in human cases are expected.

Part of the increase in cases may be due to a greater awareness among health professionals and more frequent hantavirus testing. However, in many forest and agricultural regions of Belgium, France and Germany, an increase in the population density of rodents, especially voles, has been observed since the autumn of 2004, with no sign of this increase abating.

Puumala hantavirus is the most common human hantavirus infection in Europe. It is transmitted to humans by inhalation of virus particles within rodent excretions (urine, faeces or saliva) or directly from a bite or contamination of a wound. Rodents are unaffected by the virus but remain lifelong carriers. Human to human transmission is very rare. An earlier case-control study of Belgian and French cases from 1996 identified risk factors of living less than 50 m from a forest and seeing rodents in or around the home, spending long periods in the forest, and being in contact with wood [2]. Tourist activities such as walking in woodland did not pose any risk.  

In comparison with hantavirus that may be found in other parts of the world, Puumala hantavirus usually causes mild disease. Symptoms typically occur one to four weeks following exposure and include fever, headache, myalgia, gastrointestinal upset, eye pain and blurred vision. Severe illness with hantavirus is characterised by haemorrhagic fever with renal disease or by pulmonary failure. The clinical diagnosis is confirmed by serological detection of antibodies. No specific treatment is available and most cases resolve spontaneously over two to three weeks.  Renal and/or lung complications require appropriate supportive hospital treatment.

In affected countries, information about the disease and recommendations for avoiding infection have been issued by the ministries of health. This is being distributed to travellers at camping sites, leisure and tourist information centres.

Preventative measures consist of avoiding rodents, rodent control, disinfection of places used by rodents, and measures to avoid attracting rodents such as keeping food covered.. When handling rodents or articles that may have come into contact with rodents, protective clothing and masks can be worn.

Travellers and those living in endemic areas should be aware of the risk of hantavirus, how infection is acquired and the clinical symptoms. They are advised to seek medical attention and report their risk exposure if they develop symptoms consistent with those described above.

References

1. Mailles A, Abu Sin M, Ducoffre G, et al. Larger than usual increase in cases of hantavirus infections in Belgium, France and Germany, June 2005. www.eurosurveillance.org/ew/2005/050721.asp

2. Crowcroft NS, Infuso A, Ilef D, et al. Risk factors for human hantavirus infection: Franco-Belgian collaborative case-control study during 1995-6 epidemic. BMJ 1999 318:1737-1738.