Published Date: 2012-05-25 12:18:03
Subject: PRO/AH/EDR> Hantavirus update 2012 - Europe: Germany, Slovenia
Archive Number: 20120525.1144830

HANTAVIRUS UPDATE 2012 - EUROPE: GERMANY, SLOVENIA
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In this update:
[1] Germany (Baden-Wuerttemberg)
[2] Slovenia

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[1] Germany (Baden-Wuerttemberg)
Date: Thu 24 May 2012
Source: Eurosurveillance Edition, 17(21) [edited]
http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=20180


Rise in the number of notified human hantavirus infections since October 2011 in Baden-Wuerttemberg, Germany
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[Authors: Boone I, Wagner-Wiening C, Reli D, Jacob J, Rosenfield UM, Ulrich RG, Lohr D, Pfaff G]

Summary
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From October 2011 to April 2012, 852 human hantavirus infections were notified in Germany, of which 580 (68 percent) were in Baden-Wuerttemberg. Case numbers started to rise earlier than they did before the previous outbreaks in 2007 and 2010, and are the largest ever reported in this state during October to April of any year. The early rise could be due to a beech mast year in 2011, followed by an early and massive reproduction of the reservoir bank vole populations during winter 2011 and spring 2012.

Outbreak description
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From October 2011 to April 2012 (reporting weeks 40 2011 to week 17 2012, ending 27 Apr 2012), 852 cases of hantavirus infections meeting the national case definition were notified in Germany (cumulative incidence: 1.04 per 100 000 population). Of these, 580 cases (68 per cent) originated in the southern federal state of Baden-Wuerttemberg (cumulative incidence: 5.4 per 100 000 population). This count exceeds the number of cases observed during the months October to April that preceded the outbreaks in 2007 (172 cases) and in 2010 (327 cases) in the same state. We report on this ongoing outbreak in Baden-Wuerttemberg, taking into consideration cases notified from October 2011 to April 2012.

Background
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Puumala virus is the predominant human pathogenic hantavirus species in western, central, and northern Europe. It is transmitted to humans by exposure to excreta of its rodent reservoir, bank voles (_Myodes glareolus_). After an incubation period of usually 2-4 weeks, typical clinical manifestations include a sudden onset with fever, headache, back pain, and gastrointestinal symptoms. Renal involvement is prominent and manifests initially as oliguria and later as marked polyuria (nephropathia epidemica). Only 30 per cent of Puumala virus infections occur with typical clinical signs, resulting in high under-reporting. There is currently no specific antiviral treatment. Recommended prevention measures focus on the avoidance of exposure and inhalation of potentially contaminated dust.

In Germany, laboratory-confirmed cases of hantavirus infections have been notifiable since 2001 [1,10]. Between 2001 and 2011, the number of annual notifications ranged from 72 to 447, with a median of 235, except for 2 outbreaks in 2007 (1688 cases) and 2010 (2107 cases). From November 2011 to February 2012, the Robert Koch Institute observed an increase in the number of cases notified in Germany compared with the mean in the same period in the 5 preceding years, from 2006/2007 to 2010/2011. Some 64 per cent of these cases were reported from Baden-Württemberg.

Discussion
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The causes for the early increase of case numbers remain unclear. Current hypotheses relate the rising incidence of Puumala virus infections to changes in the population density of bank voles, due to climatic factors [12] and possibly to the beech mast in 2011. During mast years, deciduous trees produce exceptionally high quantities of seeds, an important food source for bank voles [14]. Mast years and hantavirus outbreaks appear to be associated [15,16]. In Baden-Wuerttemberg, the beech mast years of 2006 and 2009 were followed by outbreaks of human hantavirus infections in 2007 and 2010. Last year (2011) was again an exceptional mast year [17], followed by a remarkably mild winter [18]. This may have promoted winter survival and reproduction of bank vole populations.

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ProMED-mail
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[As indicated above, these cases involve Puumala hantavirus and bank voles. The discussion above suggesting that abundant food for the voles (beach mast crop) leads to increased vole population densities with increased Puumala virus transmission is reasonable. Future prospective field studies would be of interest to see if there would be additional data to support these earlier associations of food availability and vole abundance.

An image of _Myoides gareolus_, the Puumala virus host, can be accessed at http://www.wildabouttheworld.com/gallery/showphoto.php?photo=7172

A HealthMap/ProMED-mail interactive map of Germany can be accessed at http://healthmap.org/r/2rKM. - Mod.TY]

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[2] Slovenia
Date: Thu 24 May 2012
Source: Eurosurveillance Edition, 17(21) [edited]
http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=20176


Increased number of cases of haemorrhagic fever with renal syndrome in Slovenia, January to April 2012
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[Authors: Kraigher A, Frelih T, Korva M, Avsic T]

Summary
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Haemorrhagic fever with renal syndrome is endemic in parts of Slovenia. Since 1999, in January-April each year, the number of notified cases has generally been low (n=0–6). A high number of cases (n=26) in the 1st 4 months of 2012 has been observed, similar to that seen in the same period in 2008 (n=14). Given the increase in the number of cases at the start of 2012, we can expect a high number of cases this year.

Situation at the beginning of 2012
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From 1 Jan to 18 Apr 2012, 26 cases of haemorrhagic fever with renal syndrome (HFRS) were notified in Slovenia: 7 in January, 6 in February, 3 in March, and 10 in April. The patients (19 male, 7 female) ranged in age from 21 years to 75 years (interquartile range: 33-57 years). This number of cases for the 4-month period is unusually high and may herald an increased number of cases this year.

Background
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Viruses of the genus hantavirus, family _Bunyaviridae_, are the causative agents of HFRS. They are most commonly acquired from inhalation of aerosolised excreta from acute and chronically infected rodent hosts.

The disease was first reported in Slovenia in 1954. Since then, cases have occurred sporadically or in small epidemics. Mandatory reporting of laboratory-confirmed HFRS cases is enforced by the Contagious Diseases Act issued in 1995. Both mild and severe clinical courses of the disease have been observed, with an overall mortality rate of 3.3 per cent.

Dobrava and Puumala viruses -- 2 hantaviruses that cause HFRS -- have been shown to coexist in Slovenia. There are considerable differences in disease severity as well as mortality due to infection with these viruses: all fatal HFRS cases in the country to date have been caused by infection with Dobrava virus, giving an 8.3 per cent mortality rate for Dobrava virus-associated HFRS. Infection with Puumala virus usually results in a milder disease course.

Although HFRS patients have been found throughout the country, most of them have been reported in the endemic regions of Novo Mesto, Murska Sobota, and Ljubljana.

Discussion
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Since 1999, with the exception of 2008, the majority of HFRS cases each year have been reported in late spring and summer. Probable reasons for the increase in the number of HFRS cases in the 1st 4 months of 2012, as in 2008, are the mild winter and an abundance of available oak and beech seeds [mast] in the preceding summer and autumn. The bank vole (_Myodes glareolus_), the principle vertebrate host for Puumala virus, and the yellow-necked field mouse (_Apodemus flavicollis_), the principle vertebrate host for Dobrava virus, are predominantly seed eaters.

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[It will be interesting to see if the prediction of increased cases occurs over the next 4 months, or if the public information campaign that has been launched will prevent that from happening.

An image of _Apodemus flavicollis_, the host of Dobrava virus can be accessed at http://www.naturephoto-cz.com/yellow-necked-field-mouse-photo-2605.html.

A HealthMap/ProMED-mail interactive map of Slovenia can be accessed at http://healthmap.org/r/1JDK. - Mod.TY]

See Also