After more than a week of confusion, the World Health Organization confirmed on Monday that a man in southern China has been infected with the SARS virus.
The 32-year-old TV producer is in stable condition and none of the 81 people he had contact with have so far developed symptoms of the respiratory disease. However, worried WHO officials “don’t have a clue” about how he contracted the virus.
“From what we can tell he had no contact with civets or animal markets,” says Dick Thompson, a WHO spokesman. The SARS virus has been detected in palm civets, a raccoon-like animal, and other exotic animals eaten in China. “He didn’t travel, he didn’t have contact with healthcare workers – all the things that would suggest a possible source of infection.”
Nonetheless, Chinese officials have ordered all local wildlife markets to shut down and called for the extermination of civets in Guangdong, the man’s home province and the original location of the 2003 epidemic. The authorities also intend to exterminate rats, flies, mosquitoes, and bedbugs.
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The WHO has warned that a mass slaughter of the civets might actually increase the risk of transmission to the people carrying it out.
Viral elements
The man, who came down with a fever and headache on 16 December, was admitted to hospital and diagnosed with pneumonia four days later. SARS was suspected and PCR tests that check for specific viral elements were positive in a few samples from the patient.
The WHO confirmation came after researchers compared blood tests done early in the man’s illness with those done more recently. In these virus neutralisation tests, scientists add a live SARS virus to a sample of the patient’s blood.
If the patient has been exposed to SARS, antibodies in the blood will attack the virus. In this case, the number of antibodies increased over time, as would be expected if the man was infected with SARS.
“We’ve got a few PCR positives and the virus neutralisation,” Thompson told New Scientist. “But the gold standard is to isolate the virus, sequence it, and compare it to known SARS viruses,” of which there are dozens, he said. “We’re working like heck to isolate this virus but so far we haven’t been able to do it.”
However, scientists at Hong Kong University announced on Monday that they had sequenced some important viral genes from samples taken from the infected man, and found them to be very similar to previous SARS coronaviruses.
New strain
According to reports, Chinese scientists have also found a close similarity between the SARS virus in this latest case and a virus found recently in a civet.
The two viruses “may be of the same lineage and are different from the animal or human SARS-like coronavirus found last year,” said Zhong Nanshan, head of the Guangdong Institute for Respiratory Diseases. “This indicates that another sub-lineage of SARS-like coronavirus has again jumped from wild animals into humans over the past few months.”
Chinese press reports have also suggested that rats in the man’s apartment building tested positive for the virus.
The WHO declared the human-to-human transmission of SARS “broken” in early July, after a worldwide epidemic that claimed over 774 lives and infected more than 8000 people. Single SARS cases were confirmed in Singapore in September and Taiwan in December, but both were traced back to laboratory exposure to the virus.
Tests are currently being done on a woman in the Philippines who developed a fever after returning home from Hong Kong and a Malaysian woman who became ill after visiting Guangdong.
Thompson said the suspected cases are under investigation but downplayed concerns over a new epidemic: “We’ve been hearing about suspected cases for months now, and for the most part they’ve turned out to be influenza.”
