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Worldwide resistance to drugs used to treat influenza has increased by 12 percent since the mid-1990s, concludes a report published by The Lancet.
Adamantanes have been used to treat influenza A virus infections for more than 30 years. Previous surveillance studies have identified a low incidence of resistance to amantadine and rimantadine among circulating influenza virus strains. However, it has been 10 years since the last comprehensive global study of resistance to these drugs was published.
In the largest study of adamantane resistance to date, Rick Bright, of the Centers for Disease Control and Prevention, and colleagues screened 7,000 influenza A isolates for gene mutations known to confer drug resistance. They found that drug resistance increased from 4 percent in 19941995 to 12.3 percent in 2003-2004. They also found that 61 percent of resistant viruses isolated since 2003 were from people in Asia. Some Asian countries had drug resistance frequencies exceeding 70 percent.
Bright comments, We were alarmed to find such a dramatic increase in drug resistance in circulating human influenza viruses in recent years. Our report has broad implications for agencies and governments planning to stockpile these drugs for epidemic and pandemic strains of influenza With the increasing rates of resistance shown here, amantadine and rimantadine will probably no longer be effective for treatment or prophylaxis in the event of a pandemic outbreak of influenza.
Source: The Lancet