Drug-resistant flu detected: Japanese strains appear transmissible.For the first time, researchers report drug resistance in type B influenza virus influenza virus
Any of three viruses of the genus Influenzavirus designated type A, type B, and type C, that cause influenza and influenzalike infections. , which causes about 30 percent of flu cases in the United States. Furthermore, the researchers say that unlike a previously noted drug-resistant type A strain, this strain may jump from person to person.
"We've found a very clear case of resistance in the presence of antiviral drugs Antiviral Drugs Definition
Antiviral drugs are medicines that cure or control virus infections.
Antivirals are used to treat infections caused by viruses. ," says Yoshihiro Kawaoka of the University of Tokyo “Todai” redirects here. For the restaurant called Todai, see Todai (restaurant).
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Kawaoka's team studied flu in children infected during a 2004-2005 type B outbreak in Japan. They collected viruses before and after the children had been treated with zanamivir or oseltamivir, two drugs more commonly prescribed in Japan than elsewhere.
While no virus displayed resistance before the drug treatment, a strain from one of 74 children showed resistance to oseltamivir after treatment. This strain harbored mutations in the gene for neuraminidase neuraminidase /neu·ra·min·i·dase/ (-ah-min´i-das) an enzyme of the surface coat of myxoviruses that destroys the neuraminic acid of the cell surface during attachment, thereby preventing hemagglutination. , the enzyme targeted by the antiviral drugs. Kawaoka says that there is a good chance that resistance arose because of the drug treatment.
The team also studied viruses from 348 ill but untreated adults and children. Seven patients carried drug-resistant viruses--a surprising find. "This is good evidence that the [resistant viruses are] circulating in the community," Kawaoka says.
Three of the seven carriers may have caught the bug from siblings infected with a resistant strain. The other four probably caught it from nonfamily members in the community, the researchers say, although they acknowledge that the resistant bugs might have evolved spontaneously in the patients. All seven resistant strains carried mutations in the neuraminidase gene.
In 2004, the same research team found drug-resistant strains of the more common type A influenza in 18 children in Japan. The researchers found no evidence that those bugs could hop from person to person.
The new report suggests that drug-resistant type A strains could become transmissible transmissible /trans·mis·si·ble/ (trans-mis´i-b'l) capable of being transmitted.
Capable of being conveyed from one person to another. , a scenario that worries Anne Moscona of the Weill Medical College of Cornell University in New York City New York City: see New York, city.
New York City
City (pop., 2000: 8,008,278), southeastern New York, at the mouth of the Hudson River. The largest city in the U.S. .
In a commentary accompanying the Japanese report in the April 4 Journal of the American Medical Association JAMA: The Journal of the American Medical Association is an international peer-reviewed general medical journal, published 48 times per year by the American Medical Association. JAMA is the most widely circulated medical journal in the world. , Moscona says that earlier laboratory and animal studies suggested that drug-resistant flu strains would be less infectious and less transmissible than normal strains. The new report, though, shows that "contrary to what had been hoped until now, some resistant variants are vigorous pathogens [that] maybe here to stay," Moscona says.
Japan's reliance on antiviral medications makes the country an ideal breeding ground for drug-resistant flu strains, Kawaoka says. Both he and Moscona urge monitoring of seasonal outbreaks for further drug resistance and call for especially close scrutiny of any appearances of avian influenza avian influenza: see influenza. , a type A virus.
"Influenza viruses evolve rapidly and nimbly," Moscona says. She wants pharmaceutical companies to develop new drugs that target weak points on the influenza virus other than neuraminidase. She also says that policy makers and physicians should rethink their antiviral-medication policies to ensure that the drugs aren't overused.