The public is flooding the Centers for Disease Control and Prevention for information on severe acute respiratory syndrome, a mysterious new illness that has crossed the globe in lightning speed.
Dr. Julie Gerberding, director of the Centers for Disease Control and Prevention, told a Senate panel Tuesday the volume of daily calls to the agency from the public has at times exceeded 1,500. That's more than the CDC received even at the peak of the fall 2001 anthrax attacks, she said.
Gerberding said the CDC is trying its best to communicate with Asian communities about the virus, which is believed to have originated in Guangdong, a southern province of China. That includes telling airline workers how to protect themselves and how to decontaminate a plane that might have flown a suspected SARS patient.
The United States "has risen to the occasion," Gerberding told a Senate panel, but other nations may not be responding as well to SARS.
"It's going to be very difficult to contain it" as it spreads across the globe, she said.
Gerberding told a different Senate panel on Monday that epidemiologists are working on a vaccine for the very contagious virus and expressed hope that it will peter out on its own.
Gerberding said as it stands right now, 2,301 cases of SARS exist internationally, 148 of them in the United States. Those cases are spread over 30 states.
"This has very quickly become an international epidemic," Gerberding told the Senate Health, Education, Labor and Pensions Committee. "We don't know where this is going to go. We have to be prepared for this to continue to spread."
But, Gerberding added, "If we are lucky, it will have a seasonal pattern and wane in the summer months."
In fact, officials say the number of new cases in the past week suggests the spread of the malady has stabilized somewhat.
Scientists, however, are still baffled by the virus because it spanned the globe so quickly and because it affects people differently.
Jerry Hauer, acting assistant secretary for public health preparedness at the Department of Health and Human Services, said no one can explain why U.S. patients are less sick than Canadian patients. SARS has forced thousands of people in Toronto to be quarantined and has killed nine.
"It might be that some of these folks in Canada just got more of the virus, were in closer contact," he said. "Any theory I give you at this point in time would just be a theory."
Officials are also trying to figure out what has caused the disease. World Health Organization medical experts currently in China are pursuing a connection to animals. Experts have linked SARS to a new form of coronavirus, which causes the common cold and produces other strains in animals.
David Heymann, executive director for communicable diseases at WHO, said that even if they isolate the disease and find a vaccine, which could be a year in coming, "There's not much that can be done except cordoning [infected] areas off."
On the bright side, officials are hopeful that they will have a test for the virus in about a week that would allow laboratories to determine whether a respiratory illness is SARS or a more common cold.
China is said to have hidden the fact for months that the disease was spreading in its provinces.
U.S. officials are considering basing scientists in China permanently in order to speed up detection of diseases. China is frequently the first site for flus that spread globally in part because of the dense living space and in part because Chinese people are often forced to live in close proximity to animals that spread flu and other diseases.
"If you've got people on the ground, you have a much better sense as to what's going on," Hauer said. "I'm optimistic at this point that we will have some kind of presence after this is all over."
Dr. Anthony Fauci of the National Institute of Allergy and Infectious Disease told senators that he is concerned because of the transmissibility of the disease and the fact that it is a new virus.
"This one jumped from animal species to human, then jumped from human to human," he said.
He added that scientists have not determined yet whether the damage is made worse because of the virus itself or because of the immune system's response to it. But he said, the positive side is that the microbe causing the virus can be cultured, which makes it easier to develop a vaccine.
Gerberding added that the disease is a real challenge because it is very "unfaithful" as it evolves and replicates itself.
But, she said, full recovery is possible even though it "can be a long time in coming."
Fox News' Julie Asher and The Associated Press contributed to this report.