WEDNESDAY, April 26, 2006 (HealthDay News) -- As the fear of a potential bird flu pandemic mounts, researchers have used a computer model to figure out the best way of controlling a pandemic should it occur.
According to their model, fast treatment and isolation of infected cases and all their household contacts would be key to effective control of any flu outbreak. The model looks at a potential flu pandemic in both the United States and Great Britain.
In addition, the researchers recommend that vaccine should be stockpiled, even if the vaccine has low effectiveness. The computer simulation also shows that tight border controls and travel restrictions would only slow -- not stop -- the outbreak, even if they were firmly enforced.
All of these interventions would help put the brakes on a pandemic, however.
"This report acknowledges that even in a worse-case scenario, the preparedness being talked about will slow the spread of the disease," said Dr. Marc Siegel, a clinical associate professor of medicine at New York University School of Medicine and author of Bird Flu: Everything You Need to Know About the Next Pandemic.
He was not involved in drawing up the model, which appears in the April 26 online edition of Nature.
In their study, a team led by Neil Ferguson, a professor of mathematical biology from Imperial College London, used computer models to study the influence of anti-pandemic measures, such as treatment and prophylaxis with antiviral drugs, household quarantine, vaccination and restrictions on travel.
Some of their conclusions: "Border restrictions and/or internal travel restrictions are unlikely to delay spread by more than two to three weeks unless more than 99 percent effective. School closure during the peak of a pandemic can reduce peak attack rates by up to 40 percent, but has little impact on overall attack rates, whereas case isolation or household quarantine could have a significant impact, if feasible."
The models showed that giving antiviral drugs, both as treatment to infected cases and as prevention for family members, in addition to early closing of schools, could cut the rate of the disease spread by almost half.
But for this policy to work, there would have to be stockpiles of antivirals to treat about 50 percent of the population. That's twice the amount many countries are now planning to keep on hand, the researchers note.
However, such a stockpile, combined with the vaccination of children, might reduce illness rates by two-thirds, even if the vaccine was not completely effective. Greater drug availability would have a larger protective impact overall, the British team concludes.
These models are based on a typical strain of human influenza. However, a virus that caused more prolonged and severe disease, such as the H5N1 avian influenza virus, might be even easier to control, since the time it would take for a pandemic to develop might give health agencies more time to react, the researchers say.
Siegel said history supports the notion that isolating the sick and their families helps contain an epidemic. "It is always isolating sick people and household quarantine that is most effective in preventing the spread of disease," he said.
However, he does worry about the premature institution of quarantine and travel restrictions. "I am concerned about the timely use of public health measures," Siegel said. "I hope that people will follow isolation in an emerging epidemic, but I don't know how fear is going to factor into this -- it's unpredictable."
The expert also noted that no one can predict whether current antiviral medications will be effective against an as yet unknown mutated strain of flu. "In actual practice, using antivirals effectively is very difficult," he said.
As for vaccines, he said that getting enough vaccine to those who need it will be a tough challenge, given current vaccine production methods.
"It is going to be very hard to match the serotypes with any emerging strain when you consider that we are using an approach that requires six to nine months to make a vaccine," Siegel said.
Another public health expert warns that these strategies can only be effective if the public health community is organized and prepared. That could prove a daunting task: a team from Johns Hopkins University released a survey earlier this week that found that close to half of U.S. public health-care workers would not show up for work if a pandemic occurred.
But health-care workers will be key to beating back any outbreak, said Dr. David L. Katz, an associate professor of public health and director of the Prevention Research Center at Yale University School of Medicine. "Almost all of the potentially effective flu containment strategies require coordination among first responder agencies, clear messages, rapid and reliable communication, unambiguous chains of command, and efficient distribution of resource materials," he said.
"Absent these fundamentals of public health preparedness, no computer model will help us," Katz added.
More information
There's more on bird flu at the U.S. Centers for Disease Control and Prevention.
