Infection of grey seals and harbour seals with influenza B virus

• Published in: International Congress series 2001-10, Vol.1219, p.225-231
• Main Authors: Fouchier, R.A.M, Bestebroer, T.M, Martina, B.E.E, Rimmelzwaan, G.F, Osterhaus, A.D.M.E
• Format: Article
• Language: English
• Subjects: Animal; Ecology; Epidemiology; Reservoir
• ISSN: 0531-5131; 1873-6157
• DOI: 10.1016/S0531-5131(01)00647-1

Background: Influenza B virus is exclusively a human pathogen whose origin and possible reservoir in nature are not known. Seals in the wild are known to be susceptible to influenza A as well as other virus infections. Methods: PCR-based analyses, virus isolation techniques and serological assays were used for the detection of influenza B virus infection of seals. Sequence analysis and serology were used for virus characterisation. Results: An influenza B virus was isolated from a naturally infected harbour seal ( Phoca vitulina). The infected seal and a second seal, both of which had been admitted to a seal rehabilitation centre in the Netherlands, seroconverted to influenza B virus. Influenza virus B/Seal/Netherlands/1/99 was found to be infectious to seal kidney cells in vitro. Sequence analyses as well as serology indicated that this influenza B virus is closely related to strains that circulated in humans 4 to 5 years earlier. Retrospective analyses of sera collected from 971 seals showed a prevalence of antibodies to influenza B virus in 2% of the animals after 1995, and in none before 1995, suggesting that the virus was introduced in the seal population from a human source around 1995. Conclusions: This is the first report on natural influenza B virus infection emerging in a non-human species. The data document that influenza B virus can be maintained in seals. This reservoir, harbouring influenza B viruses that have circulated in the past, may pose a direct threat to humans in the future.