Indiscriminate use of antiviral medications to prevent and treat influenza could ease the way for drug-resistant strains of the novel H1N1 virus, or swine flu, to emerge, public health officials warn -- making the fight against a pandemic that much harder.
Already, a handful of cases of Tamiflu-resistant H1N1 have been reported this summer, and there is no shortage of examples of misuse of the antiviral medications, experts say.
People often fail to complete a full course of the drug, according to a recent British report -- a scenario also likely to be occurring in the U.S. and one that encourages resistance. Stockpiling is rife, and some U.S. summer camps have given Tamiflu prophylactically to healthy kids and staff, and have even told campers to bring the drug to camp. Experts anticipate more problems in the fall as children return to school and normal flu season draws nearer.
"Influenza viruses mutate frequently and any viral resistance could be acquired easily," said Dr. Anne Schuchat, director of the National Center on Immunization and Respiratory Disease at the Centers for Disease Control and Prevention in Atlanta. "It won't surprise us if we see resistance emerge as a bigger problem in the fall or in the years ahead."
Prescribed in pill form, Tamiflu (oseltamivir) works by preventing the flu virus from leaving infected cells and spreading to new ones. Because a vaccine against pandemic H1N1 influenza will not be widely available for several months, Tamiflu and to a lesser extent Relenza (zanamivir), an antiviral that acts similarly, are key medical tools for fighting the pandemic in the meantime.
On Friday, however, the World Health Organization advised doctors that even those who are sickened with swine flu do not need to be given Tamiflu or Relenza if they are only mildly or moderately sick and are not in a high-risk group (such as children under 5, pregnant women and those with an underlying health condition).
Both drugs can help prevent illness in people exposed to the virus and reduce illness severity in people already sickened with it. On Aug. 14, after U.S. national soccer team forward Landon Donovan was diagnosed with H1N1 flu, players, coaches and support staff of the U.S. and Galaxy teams were advised to take Tamiflu as a preventive measure.
Tamiflu was chosen a few years ago for stockpiling by the federal government to deal with future pandemics.
Health authorities in the United States and elsewhere are keeping a sharp eye on prescriptions of the drug as they prepare for a surge of H1N1 cases in the fall. The U.S. government has issued detailed guidelines on prescribing antivirals. But health professionals may not follow the recommendations or may give in to patients who pester them for prescriptions that are ill-advised, said Dr. Robert Schechter, acting chief of the immunization branch of the California Department of Public Health.
"These medicines can be very helpful to those who could get very sick," Schechter said. "But excessive use will accelerate the development of resistance and lead to the lack of a medication for everybody."
Anxiety over indiscriminate use is growing, and taking the medications cavalierly is not without consequence. British health authorities reported Aug. 2 that cases of side effects from Tamiflu had doubled in the prior week, coinciding with the July 24 launch of a program in England to provide antivirals to anyone with H1N1 influenza who requests it over the phone or online.
In the first three days of the program, 150,000 packets of Tamiflu were dispensed and 293 cases of side effects were reported. Tamiflu can cause vomiting, diarrhea and mild neuropsychiatric effects.
Some U.S. health authorities have also expressed concern over misuse of the medications. Last month, the CDC urged directors of summer camps to stop handing out Tamiflu to healthy campers.
Americans are known to hoard antivirals: A 2006 study showed that heightened anxiety over a possible avian flu pandemic caused Tamiflu prescriptions to soar 300% in 2004 and 2005.
Just as with antibiotics, of central importance to antivirals' success is taking them properly, including completing the recommended course.
However, a study published in late July found poor adherence among children in London who took Tamiflu for prevention of pandemic H1N1 in the spring.
Less than half of the grade-school-age children and only 76% of the 13- and 14-year-old students completed a full course of medication.
More than half of the children reported side effects, such as nausea, stomach cramps and trouble sleeping. Almost one in five reported a neuropsychiatric side effect, such as poor concentration, confusion or bad dreams, even though the U.S. Food and Drug Administration says neuropsychiatric side effects are rare.