UK:HANTAVIRUS

Hantavirus in England: detection of a UK strain of Seoul virus in wild brown rats (Rattus norvegicus)

Hantaviruses (genus Hantavirus, family Bunyaviridae) are a group of rodent-borne viruses with a wide global distribution. There are more than 40 recognised species of hantavirus and each species appears to be specific to a different host, and therefore limited to the host distribution [1]. At least 21 hantaviruses are confirmed to be human pathogens, four of which are known to occur in Europe (table 1) [2].
Human infection most often occurs when breathing in dried aerosolised excreta from infected rodents however the direct introduction into broken skin or conjunctiva is also a possible route of transmission. Disease in humans was first recognised in Korea in the early 1950's, although the virus was not identified until 1976 [3]. Two clinical syndromes are associated with severe disease [2]: haemorrhagic fever with renal syndrome (HFRS) in Europe and Asia caused predominantly by infection with Hantaan virus (HTNV), Dobrava virus (DOBV), Saaremaa virus (SAAV), Seoul virus (SEOV) and Puumala virus (PUUV); and, hantavirus cardiopulmonary syndrome (HCPS) in the Americas caused predominantly by infection with serotypes Sin Nombre virus (SNV) and Andes virus (ANDV). The majority of hantavirus infections in humans are likely to be asymptomatic or present with mild and non-specific symptoms including fever, headache, blurred vision, gastrointestinal symptoms and back pain.
Table 1. Known types of hantavirus associated with disease in Europe [4]

Virus	Disease	Distribution	Host species
DOBV	Severe	Eastern Europe	Apodemus flavicolis
PUUV	Mild	Europe	Myodes glareolus
SAAV	Moderate	Europe	Apodemus agrarius
SEOV	Moderate	Worldwide	Rattus norvegicus

Hantavirus is notifiable in England and Wales. Laboratory confirmation of acute cases is provided by the Rare and Imported Pathogens Laboratory (RIPL), HPA Microbiology Services Porton. Between 2009 and 2010 there were two confirmed cases with no travel history recorded: one from London and one from the Yorkshire and the Humber region. In January 2012, a second confirmed autochthonous case from Yorkshire and the Humber was reported with high titres (>10,000) and symptoms consistent with hantavirus infection (RIPL data).
Following the detection of a second case in the Yorkshire and the Humber region, in collaboration with North Yorkshire and the Humber Health Protection Unit and the HPA's Rare and Imported Pathogens Laboratory (RIPL), an investigation led by Virology and Pathogenesis, HPA Microbiology Services Porton was undertaken. Trapping and testing of rodents from the patient's home led to the detection of the first UK strain of hantavirus in wild Rattus norvegicus (brown rat) [5]. Further collaboration with the National Collection of Pathogenic Viruses (NCPV), Microbiology Services Porton, led to the culture and isolation of the virus now designated strain ‘Humber'. Complete sequencing and genetic analysis confirmed the virus was a Seoul hantavirus.
Due to the high levels of cross-reactivity between hantavirus species and the lack of viral detection in any published UK study, it has previously been impossible to confirm and identify the presence of a hantavirus in the UK. Cases are likely to be under-reported due to mild cases presenting with non-specific symptoms and a lack of awareness of hantavirus as a potential diagnosis in the absence of travel. Given that R. norvegicus are ubiquitous in the UK, research is ongoing to determine the extent of human exposure to this virus.
Further information on hantaviruses can be found on the HPA website [6].
This article is a contribution from Microbiology Research Services, HPA Porton.

References
1 . Dearing MD, and Dizney L (2010). Ecology of hantavirus in a changing world. Annals NY Acad Sci 1195, 99-112.
2. Jonsson CB, Fugueiredo LTM, Vapalahati O (2010). A global perspective on hantavirus ecology epidemiology and disease. Clin Micro Rev 23, 412-41.
3. Lee HW, Lee PW, Johnson KM (1978). Isolation of the etiologic agent of Korean Hemorrhagic fever. J Infect Dis 137, 298.
4. Vaheri A, Henttonen H, Voutilainen L, Mustonen J, Sironen T, Vapalahti O (2012). Hantavirus infections in Europe and their impact on public health. Rev Med Virol doi: 10.1002/rmv.1722.
5. Jameson LJ, Logue CH, Atkinson B, Baker N, Galbraith SE, Carroll MW, et al (2013). The continued emergence of hantaviruses: isolation of a UK Seoul virus implicated in human disease, United Kingdom, October 2012. Euro Surveill. 18(3).
6. HPA. Hantaviruses. HPA website: Home › Topics › Infectious Diseases › Infections A-Z › Hantaviruses.