[Influenza pandemic planning].
In this article the most important properties of influenza A viruses are described to understand influenza pandemics. There are at least three possibilities: (1) By reassortment between an avian and the prevailing human influenza A virus viruses with a new surface are created, against which no neutralizing antibodies are present in the human population. Such a virus can spread immediately worldwide. (2) Viruses, which have been present in the human population some time ago, reappear and infect the new generation, which has not been in contact with this virus before. (3) An avian influenza virus crosses the species barrier to humans and forms there a new stable lineage. In relation to pandemic planning, the first possibility can be more or less excluded, since the now-a-days human influenza A viruses have evolved so far away from their original source, the avian influenza viruses, that the formation of a well-growing and well-spreading reassortant is practically not possible anymore. Point two is a dangerous possibility, in that, e.g., a human H2N2 virus could reappear, which had disappeared in 1968 from the human population. The third possibility is at the moment the most dangerous situation, if, e.g., a highly neurotropic H5N1 virus from Southeast Asia crosses the species barrier to humans. An infection with such a pandemic virus presumably cannot be treated efficiently by antivirals. In such a situation only a rapid vaccination would be successful. In this respect in the last year important results have been obtained by using the reverse genetics. Meanwhile in about 50 countries there have been drawn up pandemic-preparedness plans.
Scholtissek
Christoph
C
Division of Virology, Department of Infectious Diseases, St Jude Children's Research Hospital, Memphis, TN, USA.
D000818:Animals; D000940:Antigenic Variation; D001715:Bird Diseases / Q000635:transmission / Q000821:virology*; D001717:Birds; D004189:Disaster Planning; D004196:Disease Outbreaks; D006801:Humans; D009980:Influenza A virus / Q000145:classification / Q000235:genetics / Q000276:immunology / Q000472:pathogenicity; D007251:Influenza, Human / Q000453:epidemiology* / Q000517:prevention & control / Q000821:virology; D013045:Species Specificity; D015047:Zoonoses / Q000453:epidemiology / Q000635:transmission / Q000821:virology*