Researchers Map the Global Spread of Drug-Resistant Influenza

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Researchers Map the Global Spread of Drug-Resistant Influenza

ScienceDaily (Sep. 15, 2011) — In the new movie " Contagion, " fictional health

experts scramble to get ahead of a flu-like pandemic as a drug-resistant virus

quickly spreads, killing millions of people within days after they contract the

illness.

Although the film isn't based entirely on reality, it's not exactly science

fiction, either.

" Certain strains of influenza are becoming resistant to common treatments, " said

Ira M. Longini, a professor of biostatistics in the University of Florida

College of Public Health and Health Professions, the UF College of Medicine, and

the UF Emerging Pathogens Institute. " We've been able to map out globally how

this phenomenon is happening. "

Longini is among a team of researchers who have published this month in the

Royal Society journal Interface and explain how seasonal H1N1 influenza became

resistant to oseltamivir, otherwise known as Tamiflu, the most widely used

antiviral agent for treating and preventing flu. The scientists say that a

combination of genetic mutations and human migration through air travel can lead

to the rapid global spread of drug-resistant strains.

" If you see resistant strains in parts of the world where no one is taking

antiviral drugs, that's the smoking gun that the resistant strain must be

transmitting, " said Longini, who also worked on this research at the Fred

Hutchinson Cancer Research Center in Seattle.

In some situations, drug-resistant bacteria and viruses can spread when drugs

are overused. The scientists explored this theory using a mathematical model

that simulates the spread of influenza across 321 cities connected by air

travel. Using this model, they found that oseltamivir use had not been nearly

widespread enough to promote the spread of antiviral resistance after it arose.

However, the resistant strain probably originated in one person taking the drug.

" Oseltamivir is an important prophylactic, or preventative agent, against future

flu viruses, including a potential H5N1, or 'bird flu,' pandemic, " said Dennis

Chao, the lead author of the paper and a staff scientist at the Center for

Statistics and Quantitative Infectious Diseases at the Fred Hutchinson Cancer

Research Center.

However, influenza can mutate, making the drug less effective. It had been

believed that this mutation would not spread because it makes the flu less

transmissible in people not taking the drug.

" The fact that it spread so quickly in seasonal H1N1 between 2006 and 2008 took

everyone by surprise, " Chao said.

The researchers say that the mutation may have " hitchhiked " on one or more other

mutations that made the drug-resistant influenza strain more transmissible. They

suggest that because strains of influenza turn over so rapidly, there are many

opportunities for these types of mutations to arise in an otherwise highly

transmissible strain and become widespread, and it can become the dominant

strain within a couple of years, making the drug useless.

" For the next pandemic, we should have all the available drugs at our disposal

as a first line of defense to both prevent infection and to treat the most

vulnerable, " Longini said. " Or else, the chance that the next pandemic influenza

strain is resistant goes up. We know something like 'Contagion' could happen for

influenza. "

D. Bloom of the Fred Hutchinson Cancer Research Center, and Beth F. Kochin

and Rustom Antia of Emory University are also authors of the paper.

http://www.sciencedaily.com/releases/2011/09/110914143641.htm