Re: First ever Irish case of Hantavirus confirmed
volume 13 issue 8 August 2012
Hantavirus – a visitor from the continent
A thirty year-old tourist from Germany presented in the Mid West Regional Hospital earlier this year with renal failure and respiratory symptoms. He was managed with supportive therapy and made a good recovery. He was discharged and returned to Germany. Subsequently, he was found to be IgM positive for Hantavirus and this diagnosis was confirmed by Porton Down in early June.
Human Hantavirus infection has not previously been diagnosed in Ireland. However, there were an exceptional number of cases reported in Germany and in other countries in Europe during the winter of 2011 and spring of 2012. Given the amount of travel between the continent and Ireland, it is not surprising that we would eventually see a case of this infection here. This is the first ever case confirmation that has been reported in this country and, as an unusual event, it merits further consideration.
Background
In May 2012, Health Protection colleagues in Germany reported a significant rise in the number of cases of human hantavirus infection notified there between October 2011 and April 2012. In total 852 cases had been reported, 68% of cases in the Baden-Württemberg region alone, the region that the tourist was from. The tourist also reported that his partner had had hantavirus infection in Germany last year. It was concluded, therefore, that the case confirmed in Ireland was linked to the German outbreak. This highlights the importance of continuous vigilance and of awareness of infectious diseases that are prevalent in other countries.
Epidemiology
Hantaviruses are RNA viruses, a genus of the Bunyaviridae family, and the only genus without an arthropod vector. There are more than 25 antigenically distinguishable viral species, each associated primarily with a single rodent species. Several species are known to infect humans. In particular, Seoul virus is found worldwide, Puumala virus in Europe, Hantaan virus principally in Asia and less often in Europe, and Dobrova virus in Serbia and Montenegro. Human to human transmission does not occur.
The vector
Bank voles (Clethrionomys glareolus) are the reservoir-vectors of Puumula virus, which is the cause of a mild form of haemorrhagic fever with renal symptoms (HFRS) known as nephropathica epidemica. These small rodents are found in forests and agricultural hedgerows, have a highly fluctuating population, and disperse into rural and suburban gardens and dwellings in the autumns and winters, when their population peaks. Bank voles are not native to Ireland; they are an introduced species, first documented in 1964. They are to be found in the south and west of the country.
Transmission to humans
In the case of Puumala virus, transmission is via aerosolised dust from the excreta of infected rodents
Incubation period and disease progression
The incubation period is typically 2 weeks (5-42 days). Five phases are described in very severe forms of HFSR infection; febrile (toxic), hypotensive, oliguric, polyuric followed by convalescence which may extend from a few weeks to several months.
Clinical presentation
The primary impact of hantaviral diseases is on the vascular endothelium, resulting in increased vascular permeability, hypotensive shock and haemorrhagic manifestations. Depending on the viral species, they may have a predominant effect on the kidneys (HFRS) or the lungs (Hantavirus Pulmonary syndrome - HPS).
The typical features are: fever, thrombocytopenia and acute renal insufficiency pathologically typical of acute interstitial nephritis.
Nephropathia epidemicacaused by Puumala virus is rarely haemorrhagic and is fatal in less than 0.5% of cases. Abdominal pain and hyposthenuria (urine of low specific gravity) may be manifestations. Up to 90% of Puumala virus infections are asymptomatic.
Diagnosis
Virtually all hantavirus patients have both IgM and IgG ELISA antibodies present at the time of admission. Hantaviruses are difficult to recover from cell-culture or animal hosts but can be detected by reverse transcription-polymerase chain reaction or in tissues by immuno-histochemical staining
Treatment
Supportive therapy is critical and renal dialysis may be necessary in severe cases. Studies suggest that IV ribavirin may be beneficial in management of severe HFRS. Early management of hantavirus patients should avoid excessive administration of fluids in febrile, haemoconcentrated hypotensive patients. Vascular leak leads to extravasation into retroperitoneal tissues. Cardiotonic drugs should be considered early due to the haemodynamic profile of decreased cardiac output and increased vascular resistance.
Patients with mild HFRS due to Puumala virus rarely require dialysis.
Prevention
In endemic areas, avoid contact with wild rodents as much as possible. Occupational and recreational activities may influence the risk of exposure. Rodents should be prevented from accessing houses and other buildings. Food that could attract rodents should be stored in rodent-proof conditions. Areas/surfaces that may have been contaminated with rodent excreta should be sprayed with a disinfectant prior to cleaning. Avoid aerosolisation of contaminated dust.
Discussion
Hantavirus is not notifiable in Ireland. However, the infection is ‘unusual’ in Ireland and, as such, in accordance with the Infectious Disease Regulations (1981), the Medical Officer of Health/Department of Public Health should be informed when a case is suspected or confirmed.
Hantavirus infection has not been reported until now in Ireland. Nevertheless, given the relatively long incubation period, the prevalence of the virus in continental Europe and the high level of movement between countries, it is perhaps surprising that this diagnosis is so rare in this country.
Aidan O'Hora, HPSC; Patrick O'Sullivan, HSE Midwest
http://ndsc.newsweaver.ie/epiinsight/m7wauldn4v2?a=1&p=26356355&t=17517774
