Bird Flu Alarm

Understanding Avian Influenza

Family Quarantine Is a Key to Fighting Bird Flu, Study Says

John Roach
for National Geographic News

April 26, 2006

Strict isolation of households is among the tactics touted by scientists in a new study on how to combat a bird flu pandemic.

The study recommends rapid treatment and quarantine of not only infected people but also their uninfected household contacts. Travel restrictions, school closures, and vaccines were also studied to estimate their effectiveness in mitigating an avian influenza pandemic.

The results are reported in tomorrow's issue of the journal Nature.

The study is one of a series examining potential pandemic-fighting strategies and is funded by the National Institute of General Medical Sciences in Bethesda, Maryland.

Jeremy Berg, director of the institute, said the development of several models for a flu pandemic is similar to the use of several models to forecast the weather.

"When the National Hurricane Center is predicting where a hurricane might hit land, they run lots of different models, and only once they start coming up with a similar answer do you get confidence they might know what's going on," he said.

The models "are not a substitute for policy development in any sense," Berg added. "They inform policymakers in ways that are hard to do without them."

The current study, he said, is particularly useful when looking at the impact of multiple tactics.

Cocktail Ingredients

In addition to rapid treatment with antiviral drugs and isolation of entire households, the study recommends coupling the treatments with early closure of schools hit by the outbreak.

This would reduce disease rates by nearly half, according to the models.

However, for this strategy to work, antiviral stockpiles need to be sufficient to treat 50 percent of the population?twice the number many countries are planning for.

The United States currently has enough antiviral drugs to treat one percent of the population, according to Neil Ferguson, lead author of the study. Ferguson is a professor of mathematical biology at Imperial College in London.

Other effective measures include keeping a vast stockpile of vaccine on hand, even if it's not perfectly matched to the outbreak strain, the researchers write.

Combined with an antiviral drug strategy, infection rates could be reduced by two-thirds, according to the results.

Border controls, however, are unlikely to delay the spread of influenza by more than a few weeks unless there is more than 99 percent compliance.

That level of compliance is difficult and costly to enforce in today's highly mobile society, Ferguson says.

Different Strategies

"Frankly, different countries will be in different positions to implement one or more legs or arms of a combination strategy," Ferguson said.

For example, since Europe has greater stockpiles of antiviral drugs than the U.S., European countries can more aggressively pursue preventive treatment, he said.

Unless the U.S. can build its own stockpiles, the country should rely on a policy of social distancing: closing schools and telling infected people and their families to stay home, for example.

While social distancing will not stop people from getting ill, it may slow the disease spread, allowing researchers time to ramp up the vaccine manufacturing.

Prolonged and Severe

Ferguson and his colleagues' computer model assumed a strain of human influenza like the 1918 "Spanish flu" virus, which killed about five million people. (See "'Bird Flu' Similar to Deadly 1918 Flu, Gene Study Says.")

Ironically, a virus that causes a more prolonged and severe disease?as some researchers suggest would be possible with a human version of the H5N1 bird flu strain?might be easier to control, the researchers said.

"If it's more severe, we will recognize cases more easily in the population," Ferguson said.

"That's what we saw with SARS [severe acute respiratory syndrome] in 2003: a uniformly severe disease, with people only becoming highly infectious when they were very ill."

Early recognition of cases would allow researchers time to treat and isolate individuals more readily than if the pandemic were less easily detectable and less severe, he added.

"I think the good news about influenza pandemic is it's not here and we don't know when it will be here," said Berg, of the National Institute of General Medical Sciences.

"There is an opportunity to prepare for this. It's not so imminent that efforts to prepare now are going to be in vain."

Understanding Avian Influenza