February 13, 2007

scientists comment on finding of bird flu link to Hungary

These comments followed the findings that the H5N1 bird flu viruses found in Britain and Hungry were genetically almost identical.

John McCauley, Division of Virology, MRC National Institute for Medical Research, said:

“The genetic analysis carried out by VLA has clearly shown that the virus from Upper Holton in Suffolk is very closely related indeed to viruses from Geese in Hungary. Direct transmission therefore is the most likely way in which the virus was transferred from Hungary to Suffolk. It seems very unlikely that a train of infection in wild birds could have produced two viruses so closely related.

“The influenza virus genome is in the order of 15,000 nucleotides in length and so the viruses differed by only 5 or 6 nucleotides. RNA viruses like these have a higher mutation rate than do DNA viruses and so differences in sequence are be used to trace virus evolution. The techniques that were used are more comprehensive than similar studies with most viruses, notably during the FMDV crisis in 2001 and the Classical Swine Fever Virus outbreak in UK in 2000. In those cases analysis of representative regions of the genome of the viruses were sufficient to tie each to viruses from Asia. This type of analysis is not so easy with the more stable genomes of DNA viruses.

“The ability to so quickly identify the likely route of infection is outstanding and has in this case helped those responsible for disease control amazingly.”