WHO investigating Norway swine flu mutations

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(AP) – 3 days ago

GENEVA — The World Health Organization said Friday it is investigating samples of variant swine flu linked to two deaths and one severe case in Norway, but that so far the significance of the mutation is unclear.

Norway's Institute of Public Health announced Friday that the mutation "could possibly...cause more severe disease" because it infects tissue deeper in the airway than usual.

The mutation was found in three of 70 analyzed swine flu cases, said Geir Stene-Larsen, the institute's director.

Stene-Larsen said he does not believe the mutant virus is circulating in the general population in Norway, where about 680,000 people are estimated to have been infected with swine flu to date and 23 have died.

The same mutation has been found in both fatal and mild cases elsewhere, including in Brazil, China, Japan, Mexico, Ukraine, and the United States, said WHO.

In addition, "worldwide, viruses from numerous fatal cases have not shown the mutation," the global body said. "The public health significance of this finding is thus unclear."

"Just to say that the mutated virus infects deeper tissue doesn't really tell us very much," WHO spokesman Thomas Abraham told The Associated Press. "What we really need is more clinical and epidemiological data."

WHO said the anti-viral drugs still appear to be effective against viruses with the mutation, and studies show that currently available pandemic vaccines confer protection against the variant strain.

Virus mutations occur spontaneously and many have no effect on the danger a virus poses to humans.

"Although further investigation is under way, no evidence currently suggests that these mutations are leading to an unusual increase in the number of H1N1 infections or a greater number of severe or fatal cases," said WHO.

Meanwhile the Geneva-based agency updated its global tally of deaths caused by the virus to over 6,750.

It said transmissions appear to have peaked in some parts of the United States and Western Europe, but elsewhere the number of cases is still increasing, including in eastern Europe, and Central and Western Asia.

Copyright © 2009 The Associated Press.

H1N1 flu virus mutation detected in HK

www.chinaview.cn 2009-11-24 07:33:52

HONG KONG, Nov. 23 (Xinhua) -- Hong Kong's Department of Health announced Monday that it had found the same mutation in a H1N1 flu virus sample as the one detected in Norway recently.



The department said that it had examined the genetic sequence of H1N1 flu viruses in its monitoring system. Out of the 123 sequences studied, one sample showed the same mutation as the Norway strain.



The virus was taken from a year-old boy who developed flu-like symptoms July 22. He was admitted to Prince of Wales Hospital July25 and discharged three days later. He has recovered.



Mutations are frequently encountered in influenza viruses. According to the World Health Organization, the same mutation of the virus has been found on the Chinese mainland and in other countries, including Brazil, Japan, Mexico, Ukraine and the United States.



The virus with this mutation remained sensitive to antiviral drugs, Tamiflu and Relenza. No evidence suggests these mutations are leading to an unusual increase in the number of H1N1 flu infections or a greater number of severe or fatal cases.

Mutated swine flu found in tot
Mary Ann Benitez
Tuesday, November 24, 2009

EXCERPT

The Department of Health announced last night that it found the same mutation in the boy, who developed symptoms on July 22 and tested positive for the virus on July 25 when he was admitted to Prince of Wales Hospital.



He was discharged on July 28 and recovered completely. His family members did not fall ill.



A department spokesman said: "The virus with this mutation remained sensitive to antiviral drugs oseltamivir [Tamiflu] and zanamivir [Relenza]."



The spokesman said there is no evidence that these mutations are leading to an unusual increase in the number of swine flu infections or a greater number of severe or fatal cases.

<SNIP>



Stene-Larsen added: "Based on what we know so far, it seems that the mutated virus does not circulate in the population, but might be a result of spontaneous changes."

Mutation in the Haemagglutinin gene of pandemic Influenza A(H1N1)v reported from Norway

The Norwegian Institute of Public Health reported on 20 November 2009 the detection of a mutation in the viruses affecting three cases of severe pandemic Influenza A(H1N1)v infection.



Overall approximately 70 influenza viruses from ill patients have been sequenced in Norway, including six from patients who died. The three viruses with this mutation were isolated from the first two fatal cases of pandemic influenza in Norway and one patient with severe respiratory disease.



The two fatal cases , who were not epidemiologically linked, died in July and August, 2009. Based on the currently available information it appears that the mutated virus is not circulating in the Norwegian population, but may the result of a spontaneous change occurring in severely ill patients [1].



In a note responding to the report from Norway WHO reported that worldwide, a similar mutation has been was detected in viruses from several other countries, with the earliest detection reported in April. In addition to Norway, the mutation has been observed in Brazil, China, Japan, Mexico, Ukraine and the USA.[2]

Link1

Link2

The amino acid change in the haemagglutinin HA1 gene at position 222 (225 in influenza H3 numbering) from aspartic acid (D) to glycine (G) observed, may influence receptor binding specificity and therefore has the potential to affect the pathogenicity of the virus.



This might allow the mutated virus to infect tissues deeper in the respiratory tract, although the receptor binding preferences have not been determined yet. Currently, there is no evidence about the consequences of this mutation on the biological properties of the virus.



In addition, if the receptor preference of the mutated virus corresponds to the deeper airways, this most likely will tend to reduce the likelihood for easy human-to-human spread. A likely explanation of this finding is that it is an adaptive mutation of the virus.



At this moment there is no indication of change in the virulence of the circulating pandemic Influenza A(H1N1)v virus. The virus with this mutation remains sensitive to oseltamivir and zanamivir. Studies show that the currently available vaccines confer protection.



Continued close virological monitoring in particular of severe cases, is needed to elucidate any potential relationship between the mutation and the clinical outcome of infection.