WHO says more cases of resistant to anti-virals for curing pandemic influenza

Those resistant cases occurred in a single ward in a hospital, and both involved patients whose immune systems were severely compromised or suppressed.

Transmission of resistant virus from one patient to another is suspected in both outbreaks.

The emergence of drug-resistant influenza viruses in severely immunosuppressed or immunocompromised patients undergoing antiviral treatment is not unexpected and has been well documented during seasonal influenza.

Virus replication can persist in such patients for prolonged periods of time despite antiviral treatment, creating an environment in which drug-resistant viruses can readily be selected.

This phenomenon has also been observed for the pandemic (H1N1) 2009.

Upon receipt of the reports, WHO organized a telephone conference with officials and staff from the hospitals and experts in clinical medicine, epidemiology, and virology to discuss the two outbreaks.

Particular attention is being given to the best treatment options for immunocompromised patients who become infected with the pandemic virus.

The Wales outbreak, which was detected in late October, involved eight patients. All of these patients were hospitalized because of severe haematological disorders. No deaths occurred. Three of these patients remain in hospital, with one being treated in intensive care.{mospagebreak}

In the US outbreak, which involved four severely immunocompromised patients, cases occurred in a two-week period between mid-October and early November. Three of the four cases were fatal, but the role of H1N1 infection in contributing to these deaths is uncertain.

All of the resistant viruses carried the same H275Y mutation, indicating resistance to oseltamivir but susceptibility to the second antiviral drug, zanamivir.