Health experts question flu epidemic estimates
WASHINGTON – Government projections that as many as 1.9 million Americans could die in a global flu epidemic amount to a guess that could prove to be highly inaccurate, several public health experts say.
“The problem with all the numbers is that nobody knows,” said Dr. Arnold S. Monto, a University of Michigan epidemiologist. “I try to avoid coming up with these numbers as much as possible. I know they are based on imperfect information, extrapolating from the past.”
The figures in a draft of the government’s pandemic preparedness plan have heightened public alarm about a highly virulent strain of bird flu from Asia that could undergo a genetic mutation, allowing it to become easily transmissible between humans.
While agreeing that preparation for a pandemic must be an urgent national priority, Monto and other experts say the death toll cannot be reliably estimated at this point, because no one knows how lethal a mutation of the virus might turn out to be.
“Usually, as a virus adapts to human-to-human transmission, it becomes less virulent,” said Ira M. Longini Jr., who analyzes flu and other types of epidemics as a biostatistics professor at Emory University. “A virus that kills the host cannot transmit itself as well. From the virus’ point of view, it wants the host to live.”
The worrisome strain of bird flu, known as H5N1, has spread rapidly among domestic and wild birds in Asia. More than 100 people have been infected with it, and about half have died. But in virtually all the cases, the human victims are thought to have caught the virus directly from birds.
Perhaps the clearest indication of uncertainty in the estimates comes from the government itself.
Just last year, the Department of Health and Human Services estimated that a flu pandemic could cause 89,000 to 207,000 deaths. Those numbers were contained in an earlier draft of the national pandemic preparedness plan.
The new draft, first reported by the New York Times, estimates 209,000 to 1.9 million deaths.
A spokeswoman for the department declined to discuss the difference in the estimates, suggesting that the latest numbers are now under review.