Meeting the Challenge of Bird Flu

Bird Flu (a State Dept./IIP webpage)

22 December 2005

(Best treatment option for pandemic influenza might become ineffective)

Washington –The strain of avian influenza that has caused 139 cases of human illness in Asia is developing resistance to one of the few drugs available to treat infected people, according to research published December 22 in the New England Journal of Medicine (NEJM).

People infected with the highly pathogenic H5N1 influenza strain admitted to hospitals in Ho Chi Minh City, Vietnam, were subjects of the research.

Vietnam has reported more human cases of the disease than any of the other four nations where people have fallen ill. Of 139 cases now documented by the World Health Organization, 93 have occurred in Vietnam, with 42 deaths.

Researchers have analyzed two cases of patients who have died of H5N1 virus infection, despite early treatment with the drug oseltamivir, an anti-viral medication sold under the brand name Tamiflu®.

The research team concluded that the virus’ capability to develop resistance to the drug could emerge during what currently is considered the proper treatment regimen.

The research was conducted jointly by an Oxford University clinical research unit, Ho Chi Minh City’s pediatric hospital and the London-based Hospital for Tropical Diseases.

A key finding of the work focuses on a 13-year-old girl who went to a hospital in January with a one-day history of fever and cough.

The child’s mother died of H5N1 infection the day before, so the girl was immediately suspected to be suffering from the bird flu virus. Doctors gave her oseltamivir.

It had been established previously that oseltamivir treatment is most effective when the patient receives the drug at the earliest appearance of symptoms.

That can be difficult to do when the first signs of H5N1 illness are similar to other common respiratory diseases. So the 13-year-old girl in Ho Chi Minh City was receiving optimal treatment with the anti-viral medication. She died.

“These observations suggest that the development of drug resistance contributed to the failure of therapy, and ultimately, the death of this patient,” according to the NEJM article.

A second patient similarly treated with oseltamivir also succumbed to what had become a drug-resistant virus. The researchers identified the precise genetic mutation that allows the virus to resist the effects of oseltamivir.

The research has broad and difficult implications as international health officials try to plan for a possible human influenza pandemic.

If H5N1 becomes contagious among humans, it is considered a viral strain that could start a pandemic, which would have broad human, social and economic consequences.

In recent months, national and international health leaders have been trying to raise awareness about the possibility of such widespread disease and urge a higher level of preparedness.

Building stockpiles of Tamiflu is one step many nations have included in their plans. At the same time, as more media attention is focused on the issues, individuals are clamoring to accumulate a home supply of the drug.

Medical experts are saying the possibility of unsupervised use of Tamiflu in the midst of a pandemic raises the prospect of even greater trouble.

“Improper use of personal stockpiles of oseltamivir may promote resistance, thereby lessening the usefulness of our front-line defense against influenza, and should be strongly discouraged,” said Dr. Anne Moscona of Cornell University, in an NEJM editorial that accompanied the research.

For additional information on avian influenza and efforts to combat it, see Bird Flu.