A new University of Colorado at Boulder study shows the resistance of the avian flu virus to a major class of antiviral drugs is increasing through positive evolutionary selection, with researchers documenting the trend in more than 30 percent of the samples tested.

Influenza’s ability to resist the effects of cheap and popular antiviral agents in Asia and Russia should serve as a cautionary tale about U.S. plans to use the antiviral Tamiflu in the event of widespread avian flu infection in humans, scientists say.

The antiviral drug, valganciclovir, can lower the levels of Epstein-Barr virus in children with liver transplants, according to a new study. About half of young transplant recipients with detectable levels of the virus in their blood responded to a long course of the therapy, with 60 percent maintaining their response when they stopped taking the drug. These findings are in the August issue of Liver Transplantation, a journal by John Wiley & Sons.

In this week's BMJ, a senior doctor advises caution over the use of the antiviral drug oseltamivir (Tamiflu).

Use of certain common antiviral drugs during a recent influenza B epidemic in Japan showed the development of viruses with partial resistance to the drugs, according to a study in the April 4 issue of JAMA.