Antivirals may conceal avian influenza

Menno de Jong, a virologist at an Oxford University clinical research unit in Ho Chi Minh City, Vietnam, told Bloomberg News this week that avian influenza may go undetected in patients who take the drug days before testing.

Some countries are responding to local human H5N1 avian influenza outbreaks by distributing oseltamivir to local citizens. For example, Indonesia's health ministry distributed the drug to 2,100 villagers in Garut, a district in West Java, Indonesia, where three recent cases have been documented and authorities are investigating the possibility of human-to-human transmission.

Antiviral drugs such as oseltamivir are designed to reduce the duration of viral replication and should be taken within 48 hours of symptom onset, according to WHO recommendations. However, De Jong's team, which observed 18 cases in Vietnam, found that analysis of nasal and throat swabs taken from patients 48 to 72 hours after beginning oseltamivir treatment was unable to detect the virus.