WASHINGTON (Reuters) – The U.S. government said on Monday it was releasing an experimental test for SARS, just as the World Health Organization said such tests remain unreliable.
WASHINGTON (Reuters) – The U.S. government said on Monday it was releasing an experimental test for SARS, just as the World Health Organization said such tests remain unreliable.Severe Acute Respiratory Syndrome, which has infected more than 8,000 people worldwide and killed 770, is caused by a new virus called the SARS coronavirus. It seems to have emerged only in November, in southern China, so scientists are struggling to understand it.Being able to test for the contagious disease is essential to controlling its spread, not least because SARS looks like many other respiratory illnesses. The symptoms are vague and include fever, sometimes cough, and pneumonia.The moment researchers identified the coronavirus that causes SARS they started work on tests. But it takes 10 to 21 days to develop antibodies against the virus — far too late to use an antibody test as a screening test.Pieces of the virus can be detected using polymerase chain reaction or PCR, and the “rapid” tests now available use this method. But they can often miss the virus in the early stages of infection.The U.S. Centers for Disease Control and Prevention said it was distributing an experimental PCR test to about 100 labs. The CDC cautioned that no one is sure how well it works.”Because information about the test’s performance is still being collected, patients will be asked for written consent before the test is used,” the Health and Human Services Department, which oversees the CDC, said in a statement.Researchers have said they still do not know whether it is best to test blood, sputum or tissue for the virus and the WHO said in a statement that it is not clear how soon after infection the virus shows up in the body.”The development of commercial diagnostic tests for SARS has progressed more slowly than initially hoped,” WHO said in a statement posted on its Internet site (http://www.who.int).”Part of the problem arises from certain unusual features of SARS that make this disease an especially difficult scientific challenge,” it added.Most viruses build up quickly after infection and the highest levels are seen right away. But, WHO said, “SARS, however, follows a different pattern. During the initial phase of illness, virus shedding is comparatively low.”Yet it is possible SARS patients can infect others right away — thus the urgent need for a highly sensitive test.”Such tests do not yet exist,” WHO said. “Because small quantities of the virus are initially shed, available tests, though developed with impressive speed, are unable reliably to detect SARS virus or its the genetic material during the earliest days of illness.”WHO said doctors should still use clinical definitions to diagnose SARS — which include fever, shortness of breath or a dry cough and a certain pattern of lung x-rays, as well as a history of travel to a SARS-affected area or contact with a SARS patient.WHO also said it was arranging for training courses in China — hardest hit by SARS — to instruct doctors on how best to use the available tests.(Source: Reuters, Mon June 2, 2003 05:26 PM ET, By Maggie Fox, Health and Science Correspondent)