Odd swine flu feature: No fever in some cases

Many people suffering from swine influenza, even those who are severely ill, did not have fever, an odd feature of the new virus that could increase the difficulty of controlling the epidemic, said a leading U.S. infectious-disease expert who examined cases in Mexico last week.

Fever is a hallmark of influenza, often rising abruptly to 104 degrees at the onset of illness. Because many infectious-disease experts consider fever the most important sign of the disease, the presence of fever is a critical part of screening patients.

But about a third of the patients at two hospitals in Mexico City where the U.S. expert, Dr. Richard Wenzel, consulted for four days last week had no fever when screened, he said.

"It surprised me and my Mexican colleagues, because the textbooks say that in an influenza outbreak the predictive value of fever and cough is 90 percent," Wenzel said from Virginia Commonwealth University in Richmond, where he is chairman of the department of internal medicine.

While many people with severe cases went on to develop fever after they were admitted, about half of milder cases did not; nearly all patients had coughing and malaise, Wenzel said.

Also, about 12 percent of patients at the two Mexican hospitals had severe diarrhea in addition to respiratory symptoms like coughing and breathing difficulty, said Wenzel, who is also a former president of the International Society for Infectious Diseases.

Wenzel said he urged his Mexican colleagues to test the stools for the presence of the swine virus, named influenza A (H1N1). "If the virus goes from person to person and there is virus in the stool, infection control will be much more difficult," particularly if it spreads in poor countries, he said.

Complicating matters, five different flu viruses have been circulating in Mexico simultaneously in recent months, he said.

Pneumonia rates at one of the hospitals Wenzel visited — the National Institute for Respiratory Diseases — reached 120 per week recently compared with 20 per week in the past two years, suggesting a possible relation to swine flu.

The pneumonias that the flu patients developed did not resemble the staphylococcal lung infections that were believed to be a common complication in the 1918-1919 influenza pandemic, Wenzel said.

He said the two Mexican hospitals were well-prepared for an outbreak. "We have a lot to learn from the Mexican experience," he said.

For example, when the first cases were detected and the virus seemed particularly severe, Mexican doctors activated a program to allay anxiety among staff members.

Hospital officials made it clear they would care for staff members, offering them information, a hotline, psychological support and medical examinations.

"This aspect of epidemic response is not well-appreciated in the United States yet is critical for success," Wenzel said. "We haven't put nearly enough into managing fear among health workers."

Hospital officials had good measures to screen workers and arriving patients, including supplies of alcohol sponges for people to clean their hands. Healthy nonessential workers were told to go home. Hospital officials also made sure there were enough breathing machines and oxygen canisters for patients in respiratory distress.