Researchers release report on flu antiviral resistance

Influenza antiviral resistance was found to be uncommon in influenza patients, according to the first three years of a study published in Clinical Infectious Diseases.

The Influenza Resistance Information Study was initiated in 2008 to study resistance to neuraminidase inhibitors and clinical outcome. Neuraminidase inhibitors are a class of antiviral drugs that block the function of a virus' neuraminidase protein and prevent the virus from reproducing. The study was launched after the emergence of naturally occurring resistance to oseltamivir, a type of neuraminidase inhibitor, in A/H1N1 viruses, Clinical Infectious Diseases reports.

The researchers conducted tests on 1,799 influenza-positive patients to determine the type of influenza, the subtype of influenza and any NAI resistance. Of the 1,799 patients, 1,281 had influenza A and 518 had influenza B.

Antivirals were given to 1,041 patients. All 26 of the patients treated with antivirals with seasonal H1N1 influenza had strains that were genotypically and phenotypically resistant to oseltamivir. No genotypic resistance was detected in the day one samples of any other viral subtype. Mutation-specific resistance to oseltamivir was found in 19 patients post-baseline, 14 of whom were children under the age of five.

There was no emergent resistance detected in patients with influenza B infections, Clinical Infectious Diseases reports.

The first three years of IRIS found that emergent resistance to oseltamivir in influenza viruses during treatment was uncommon at 2.2 percent and mostly found in patients between one and five years old. Viral loads were low in many cases and the clearance of the virus was rapid.