Research, Too

But Chinese health specialists, like counterparts around the world, have been busy researching the disease as well. A first step was to promote a fast diagnosis method for the A/H1N1 virus, preparing it for laboratories across the country by April 30.

Guo Yuanji and colleagues at the Chinese Center for Disease Control have been monitoring the transmission of the traditional swine flu virus H1N1 to humans since the early 1980s. They published a research paper, The Country's First Human Infection of Swine Flu H1N1 Virus, in the Chinese publication Disease Surveillance Journal in 1992.

The paper documented a suspected case of a 16-year-old, middle school student in Beijing with flu symptoms. The teen-ager reported to a hospital in Beijing in November 1991 and recovered two weeks later. Her serum antibody tests pointed to a close connection with the virus. However, the tests were conducted after the patient had recovered, making it impossible to pin down the virus before all clues were lost.　　

According to microbiologist Guan Yi at the University of Hong Kong, human swine flu infections were previously reported in Hong Kong in 1999 and 2002.

WHO's assessment of the latest situation May 11 said the latest outbreak is a strain of H1N1. It's a new subtype not previously detected in swine or humans that's communicable through person-to-person contact.

A/H1N1 contains an unusual mix of gene segments. The genetic sequencing of samples at the U.S. Centers for Disease Control (CDC) shows the new virus contains segments from four different viruses: some North American swine viruses, some North American avian flu, one human influenza, and two Eurasian swine viruses.

As the number of infected people around the globe grows and the WHO alert level remains high, scientists acknowledge they know little about where the virus came from, how it spreads or how it may mutate in the future. WHO decided to change the name from swine flu to A/H1N1 after finding no evidence that the virus can jump from pigs to humans.

Nevertheless, livestock specialist Cui Shangjin at the Harbin Veterinary Institute, a unit of the Chinese Academy of Agricultural Sciences (CAAS) noted that, due to its body structure, a pig can be a "mixing vessel" for a variety of viruses.

Widespread infections of traditional swine flu H1N1 and H3N2 viruses have been found in Chinese pigs for some time. In addition, pigs infected with the avian flu H9N2 and H5N1 viruses have been found, according to Tong Guangzhi, head of the CAAS' Shanghai Veterinary Institute. So although A/H1N1 has not been found among pigs in China, Chinese scientists say it's important to screen the animals as a precaution.

The fact that the H5N1 avian virus has become firmly established in poultry in some parts of the world is another cause for concern. No one can predict how the H5N1 virus will behave under pandemic pressure. At present, H5N1 is an animal virus that does not spread easily to humans and only rarely jumps directly from one person to another.

Although scientists around the globe are still trying to piece together data and reach conclusions, they expect to find little if any natural immunity to the virus. A/H1N1 appears to be more contagious than seasonal flu. The secondary attack rate for seasonal flu ranges from 5 to 15 percent, while current estimates for a secondary attack of A/H1N1 range from 22 to 33 percent.

WHO says work is under way to develop an effective vaccine against the new strain. But the task can take up to six months.

For next-stage prevention and control, Huang has called for environment management and behavior modification through traditional health strategies for fighting infectious diseases. He said these strategies should include clean water and air, nutritious and safe food, healthy housing, proper sewage and waste disposal, dependable disease tracking and control, healthy lifestyles and good personal hygiene.

"A scientific and effective prevention and control strategy for infectious diseases cannot be made until policymakers come to understand the workings of it," Huang said.