Early Treatment of H1N1 With Antivirals and Antiviral Resistance

The CDC has updated its Interim Recommendations for Clinical Use of Influenza Diagnostic Tests During the 2009-10 Influenza Season.

One of the key issues highlighted once again by the CDC includes the importance of early treatment following the onset of symptoms. According to the report, “When a decision is made to use antiviral treatment for influenza, treatment should be initiated as soon as possible without waiting for influenza test results. Antiviral treatment is most effective when administered as early as possible in the course of illness.”

WHO has also issued a brief, stressing the importance of early treatment with the antiviral drugs, oseltamivir or zanamivir, especially for patients who are at increased risk of developing complications, such as pregnant women and children, as well as those who present with severe illness.

Many health professionals however are worried by the manifestation of oseltamivir resistant viruses. Systematic surveillance conducted by the Global Influenza Surveillance Network, supported by WHO Collaborating Centres and other laboratories, continues to detect sporadic incidents of H1N1 pandemic viruses that show resistance to oseltamivir. To date, 28 resistant viruses have been detected and characterized worldwide. However, cases of oseltamivir-resistant viruses continue to be sporadic and infrequent, with no evidence that oseltamivir-resistant pandemic H1N1 viruses are circulating within communities or worldwide. Except for immunocompromised patients, those infected with an oseltamivir-resistant pandemic H1N1 virus have experienced typical uncomplicated influenza symptoms. No evidence suggests that oseltamivir-resistant viruses are causing a different or more severe form of illness.

As use of antiviral drugs continues to grow, further reports of drug-resistant viruses are certain to occur. WHO and its network of collaborating laboratories are closely monitoring the situation and will issue information and advice on a regular basis as indicated.

View the WHO brief at http://www.who.int/csr/disease/swineflu/notes/h1n1_antiviral_use_20090925/en/index.html;
and the CDC Interim Recommendations at http://www.cdc.gov/h1n1flu/guidance/diagnostic_tests.htm