A deadly, mysterious respiratory illness spread largely among health care workers in Asia could be a new strain of flu or even an exotic virus passed from animals to people, a health official said Sunday.
Probably the most feared by health experts, however, would be a new and deadly strain of flu.
The illness, which carries flulike symptoms, has killed nine people -- seven in Asia and two in North America. Its rapid spread in southeast Asia in recent weeks caused a rare worldwide health alert to be issued on Saturday.
Health officials say it may be several more days before they are able to identify the disease. However, they said several of its features suggest it is caused by a virus, which can often be difficult to pinpoint quickly.
Lab tests have ruled out some varieties of flu as well as some viruses that cause hemorrhagic fever. However, other possibilities remain, including such exotic diseases as the closely related Hendra and Nipah viruses -- both newly recognized, causing flulike symptoms and capable of being spread from animals to people.
"If it really is the flu, it could be we have a new organism that could cause a pandemic," said Dr. R. Bradley Sack, director of Johns Hopkins' international travel clinic.
Experts discounted the possibility that terrorism is the source and believe it almost certainly is a contagious infection that spreads most easily from victims to their doctors, nurses and families through coughing, sneezing and other contact with nasal fluids.
"Nothing about that pattern suggests bioterrorism," said Dr. Julie Gerberding, head of the U.S. Centers for Disease Control and Prevention in Atlanta.
Officials said they are encouraged that some recent victims seem to be recovering, although they are unsure whether that is because of the many antibiotic and antiviral drugs they have been given or simply the natural course of the disease.
Three or four patients had stabilized enough to be moved out of intensive care Sunday in Hanoi, Vietnam, although all still had breathing problems.
The World Health Organization has been aware of the outbreak for about three weeks but issued its global alert this weekend because of concern that the illness would spread to North America and Europe.
World health experts are trying to identify what has caused a new form of deadly pneumonia called severe acute respiratory syndrome or SARS. It spread first in southeast Asia and now has affected Canadians and perhaps one American who traveled to Asia.
Q: What are the symptoms?
A: A fever of about 101, coughing and shortness of breath. Other possible symptoms include headache, muscular stiffness, loss of appetite, confusion, rash and diarrhea.
Q: How quickly can someone get the disease after being exposed to it?
A: Three to seven days.
Q: How does someone catch it?
A: It appears to spread through close contact, such as between family members or between patient and doctor. Experts believe it is spread through coughing, sneezing and other contact with nasal fluids.
Q: What causes it?
A: Researchers don't know whether it is caused by a bacteria or a virus, and they may not know the answer for several more days.
Q: How is it treated?
A: Those suspected of having SARS are being quarantined. The best treatment is unclear because different medicines have been used.
Q: What are the chances of recovering from it?
A: So far there are nine fatalities among the 150 most recent cases.
Q: Where did the disease first appear?
A: SARS was first recognized in Hanoi, Vietnam, on Feb. 26. An outbreak of pneumonia of similar symptoms struck Guangdong province, China, last November and was only brought under control in mid February.
Q: Is it dangerous to travel in those regions?
A: U.S. health officials said travelers should consider postponing trips to countries at risk. Those who have traveled to Hong Kong or Guangdong province in China, or Hanoi, Vietnam, are being told to monitor their health for seven days. If symptoms develop, they are advised to see a doctor.