SARS virus mutating quickly into two forms

Hong Kong - Like a "murderer who is trying to change his fingerprints," the SARS virus is mutating rapidly into at least two forms, complicating efforts to develop a solid diagnosis and a vaccine, researchers say.

Scientists at the Chinese University of Hong Kong say they analyzed the genetic sequences of virus samples taken from 11 SARS patients and found by late March that two forms of the virus were present in Hong Kong.

One strain was detected in a woman whose illness was linked to an outbreak caused by a mainland Chinese man who spread SARS to others at a Hong Kong hotel.

The other strain came from a Hong Kong man believed to have caught it in the mainland border city of Shenzhen.

"This rapid evolution is like that of a murderer who is trying to change his fingerprints or even his appearance to try to escape detection," said Dr. Dennis Lo, a chemical pathologist at the university.

But while Lo said researchers have shown "the SARS coronavirus is undergoing rapid evolution in our population," he noted more work is needed before researchers can say whether the virus has become more infectious and lethal.

Researchers also need to find out whether people who get SARS from one strain can develop immunity to other strains, he said. If not, finding ways to better diagnose it and to develop a vaccine could be more difficult.

The World Health Organization says there's no evidence that the mutations have any effect on the disease itself. WHO scientists also say it's not surprising the SARS bug shows genetic changes, because the coronavirus family is prone to mutations.

A U.S. coronavirus expert, David Brian, at the University of Tennessee in Knoxville, agreed that a rapidly mutating SARS virus could complicate work toward a vaccine and reliable diagnostic tests.

The crucial question is where the mutations occur in the SARS virus genome, he said. If they affect the shape of an outer protein on the virus, it could hamper vaccines, which rely on training the immune system to recognize particular protein shapes, he said.

Diagnosis, meanwhile, is based on specific features of the bug's genetic sequence. So if one of the crucial features is removed by mutation, the detection kit becomes less sensitive to recognizing the virus, he said.

Hong Kong scientists are also concerned that the virus may survive in an infected person's body for at least a month after recovery. Doctors are urging patients to avoid personal contact such as hugging and kissing when they go home.

"The virus still exists in the patients' urine and stool after they were discharged. It will persist for at least another month or maybe even longer," said Dr. Joseph Sung, head of the Department of Medicine at the Chinese University of Hong Kong.

What's more, scientists here also fear that 12 people may have relapsed. The new findings raise questions as to how doctors can tell whether a patient has fully recovered, underscoring the difficulty health authorities face in tackling this new disease.

Sung, who works at the Prince of Wales Hospital, which was hard-hit by SARS, has monitored the cases of about 240 recovered SARS patients. He said none has spread the disease to others.

If recovered patients wear masks, avoid close contact with family members and are particularly careful about toilet hygiene, things should be "quite safe" in their households, he said.

Sung believes the virus can survive in the environment longer than a day. "If your saliva gets on a table surface, don't assume that it will be all right after it dries up," he said.

Dr. David Heymann, WHO's chief of communicable diseases, said the relapses are disappointing, and it's not clear what caused them. He said he hadn't heard of similar reports outside Hong Kong.

"We don't yet have the data ... as to exactly what has happened, what these people were treated with," Heymann said. He said one theory is that some relapses may have happened because patients stopped taking steroids too quickly. The steroid therapy is being prescribed in Hong Kong.

Heymann said in some other infectious diseases, it's not uncommon to find virus in body excretions after a patient's symptoms are gone.

"So it's not a new phenomenon that viruses remain, but certainly a relapse is concerning," he said. -- Reuters

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