September 16, 2010
New Zealand-based research has shown that for people who get both seasonal A(H1N1) and pandemic flu (H1N1) flu at the same time, the results are more than just feeling very ill - the combination could lead to a newer, more harmful variant of the virus which is harder to treat.
The new strain could arise if a cell is infected by both flu viruses (co-infection), one of which is drug-resistant (DR). This ability could be passed on to the non-DR virus, which, if the viruses are seasonal and pandemic flu, could lead to a drug resistant pandemic flu virus. Of particular concern is the possibility of a pandemic flu virus that is resistant to oseltamivir (Tamiflu).
Researchers looked at 11 New Zealanders who were infected in this way in 2009, and have concluded that, while co-infections are rare, the scenario is possible. The paper has been published today in the CDC's international journal, Emerging Infectious Diseases.
ESR's Dr Matthew Peacey was lead author of 'Pandemic (H1N1) 2009 and Seasonal Influenza A (H1N1) Co-infection, New Zealand, 2009.'
"Last year our influenza season began with the circulation of the regular seasonal A/H1N1 strain which is Tamiflu resistant. This seasonal A/H1N1 strain was rapidly overtaken by the worldwide pandemic A/H1N1 strain. In New Zealand there was a short 4-5 week period when both strains were circulating within the community and in some cases both strains were able to infect a single patient. When this happens influenza viruses are able to swap genes. In fact, this natural swapping of genes was how the pandemic strain came about."
"The worry here is this event could give rise to a more virulent influenza strain, such as a pandemic strain that is resistant to Tamiflu, and so needs to be monitored closely," Dr Peacey said.