Slowing the spread of a swine flu epidemic in the United States could well depend on how quickly communities can empty schools, close day care centers and shut down public gathering spots — and on whether ordinary people are willing to stay away from their neighbors.
Even though cases in the U.S. remain isolated, experts in so-called “social distancing” strategies say such measures could reduce an outbreak of potentially deadly infections by at least half, but only if steps are taken early.
“As soon as they have one or more cases, that threshold is crossed,” said Ira Longini, a national flu expert and professor of biostatistics and epidemiology at the University of Washington and the Fred Hutchinson Cancer Research Center in Seattle.
“You have to cut contact with people by 50 percent.”
By that measure, closing certain schools in New York and Texas after students came down with the virus last week was a smart move. And so was limiting exposure of additional victims confirmed in three other states. So far, the U.S. total stands at 68.
But far more wide-ranging steps affecting entire communities could become necessary if isolated clusters of infection in the U.S. expand to resemble the widespread outbreak that has sickened 26 in Mexico, where 6,000 are showing symptoms and 20 of 152 deaths have been tied to the virus.
‘We're going to have a problem’
“If it causes person-to-person transmission in the community in a virulent form, we’re going to have a problem,” said Dr. Brian Currie, an infectious disease expert at Montefiore Medical Center in the Bronx.
In that scenario, public health officials would be called upon to enact voluntary plans that could keep people away from work, out of school and in their homes for as long as it takes to quell the threat of infection.
Businesses would be advised to let workers telecommute, Longini said. Sports teams would be encouraged to cancel practices and games and parents would be urged to keep small children at home, avoiding even playgroups and parks.
In some cases, people could be advised to stay 6 feet away from others in public, said Longini, who has built elaborate computer models that demonstrate how infection slows when such plans are implemented.
In severe situations, people may be told to stay 3 feet apart to avoid the infectious spray of droplets when someone coughs or sneezes, Currie said.
He was part of three teams of researchers commissioned by the federal government to study intervention strategies and published the results last year.
“The least stringent scenarios cut the epidemic by half,” he said. “The most stringent cut it by two-thirds.”
Longini's models figured a compliance rate of about 60 percent, which allows some latitude for human nature.
"It depends on how afraid they are,” Currie noted.
Health officials in every state have submitted plans to the federal Centers for Disease Control and Prevention that rely on some form of social distancing to combat infection, alone or in combination with antiviral drugs for those who are already sick.
In extreme situations, local health officials would have the authority to quarantine households.
The measures are intended to slow spread of disease during the several months it could take to manufacture and distribute a vaccine effective against the new strain of the H1N1 swine flu — or any other new virus.
In 1918 pandemic, social distancing worked
Evidence that social distancing cuts infection comes directly from the worst flu outbreak in memory, the 1918 pandemic.
Cities that closed schools, churches and theaters during the early months of that deadly plague had peak weekly death rates about 50 percent lower than those of cities that imposed such measures later or not at all, according to a 2007 paper led by Marc Lipsitch, a professor of epidemiology at the Harvard School of Public Health.
In Mexico this week, government officials emptied museums, closed schools, canceled sports events and advised churches to not hold services. They also urged members of the close-knit society to avoid customary social greetings, such as kisses on the cheeks.
So far, the relatively few swine flu cases in the U.S. have not warranted widespread calls for social distancing. But that could change dramatically said Longini, who said that if his concern were measured on a scale of one to 10, this outbreak would be a six or a seven.
He urged health officials and the general public to remain aware of non-medical strategies that could help quell the spread of this new virus.
“I’m extremely worried,” said Longini. “We still have an opportunity to stop this, but it’s rapidly disappearing.”