The World Health Organization (WHO) said 30 April marks the end of two incubation periods and Viet Nam could thus become the first country taken off the list of those affected by SARS, which as of today has infected 4,649 people, 274 of whom have died, in 26 countries.WHO country staff attribute Viet Nam’s success to the quick initial reaction to the outbreak, including the commitment of the Vietnamese Government.Viet Nam was the second country to suffer a SARS outbreak after China, where an outbreak began in Guangdong Province in mid-November of last year. But the ailment was first identified by Carlo Urbani, a WHO infectious disease specialist, who alerted the world when cases of an unusual and severe respiratory illness began appearing among health staff treating a Chinese-American businessman at the French Hospital in Hanoi.The patient’s recent travel history had included trips to Guangdong. By 20 March, at least 22 staff at the Hanoi hospital were ill with influenza-like symptoms and 20 had signs of pneumonia, two of them in serious condition. The businessman died in Hong Kong on 13 March and Dr. Urbani died in Thailand on 29 March.”After Carlo identified the disease, we were able to influence the hospital to take the right infection control measures very quickly,” Pascale Brudon, WHO representative in Viet Nam, said. “The first priority was to contain the disease and monitor each case.” Also today WHO urged caution in the use of diagnostic tests as test development and validation are expected to take at least another two weeks. Currently available tests are very specific but lack sensitivity, meaning negative results cannot be relied on as proof that a patient is not infected with the virus, the agency said.In the meantime, it is extremely important for national authorities to realize the tests may give a false sense of security that can allow persons carrying the SARS virus, and therefore capable of infecting others, to escape detection, WHO added. It strongly advised authorities to continue to use present clinical and epidemiological case definitions based on symptoms, and not to rely on the results of diagnostic tests. All suspect and probable SARS cases should be placed in isolation and managed according to strict procedures of infection control, it warned.