SARS Virus

The SARS crisis of 2003 was an instance when vigorous international cooperation and intervention may have successfully prevented a global health crisis. It fully showed the value of the WHO influenza surveillance network. During the near pandemic between November 2002 and July 2003, with 8,096 known infected cases and 774 deaths (a mortality rate of 9.6%). Here are the key events of the crisis. Local outbreaks of SARS infections were reported in China, Hong Kong, Taiwan, Vietnam, Singapore, Philippines, Mongolia, Canada, and the USA. A number of dead-end sporadic cases were reported in other countries who received infected visitors from affected countries.

Identification of SARS. In early Feb 2003, Guandong province in China reported 305 cases and 5 deaths caused by atypical pneumonia of unknown cause. It later transpired that Guandong was already having similar cases as early as Nov 2006. On the 19th Feb 2003, the WHO influenza network activated emergency pandemic plans after receiving a report from Hong Kong confirming a case of Influenza H5N1 infection. This proved to one of the defining events in the control of the SARS outrbreak. On the 21st Feb, a Chinese medical professor came to Hong Kong to attend a relatives wedding. He stayed at a room on the 9th floor of the Metropole Hotel. Six people who stayed on the same floor of that hotel were infected and they carried the infection to the rest of Hong Kong, Vietnam and Canada. Therefore all the cases outside China could be traced to that event. In early March - Carlo Urbani identified SARS (Severe Acute Respiratory Syndrome) as a unique clinical entity in patients who had been infected by patient in a Vietnam hospital. That patient had previously stayed on the 9th floor of the Metropole hotel. WHO was put on alert. Sadly, Urbani himself later became infected and died.

Discovery of SARS Virus. Initially, a number of agents were implicated as the causative agent, including chlamydia, metapneumoviruses, and influenza H5N1 but it soon became apparent that a new agent may be involved. The breakthrough came on 21st March when the Hong Kong university reported the isolation of an unknown virus in FRhk4 cells, and were able to demonstrate a rising antibody response against this virus by IF in patients with SARS. Furthermore, virus-like particles were seen in lung biopsies. On 22nd March, CDC reported the growth of a corona-like virus in Vero E6 cells. This was identified as a new coronavirus and PCR based diagnostic tests became rapidly available.

Properties or SARS Virus

The SARS virus is a novel coronavirus that did not belong to the previously known OC43 and 229E serogroups. It had a genome of 29,000 bases. It had some rather unusual virological aspects.



Super-spreading Events. The SARS virus is not normally highly infectious but certain individuals have spread the virus to a large number of individuals. These individuals were already known as super-spreaders but the WHO now prefer to call them super-spreading events. In Hong Kong, 3 super-spreading events are known to have occurred.


The initial diagnosis of SARS was clinical. According to the guidelines issued by the WHO, SARS may be suspected in a patient who has:
  • Any of the symptoms including a fever of 38 ˘XC (100.4 ˘XF) or more AND
  • Either a history of Contact (sexual or casual) with someone with a diagnosis of SARS within the last 10 days OR Travel to any of the regions identified by the WHO as areas with recent local transmission of SARS (affected regions as of 10 May 2003 that were parts of China, Hong Kong, Singapore and the province of Ontario, Canada).

A probable case of SARS has the above findings plus positive chest x-ray findings of atypical pneumonia or respiratory distress syndrome.

With the advent of diagnostic tests for the coronavirus probably responsible for SARS, the WHO has added the category of "laboratory confirmed SARS" for patients who would otherwise fit the above "probable" category who do not (yet) have the chest x-ray changes but do have positive laboratory diagnosis of SARS based on one of the approved tests (ELISA, immunofluorescence or PCR).

A battery of laboratory tests became rapidly available on the discovery of the SARS virus.

RT-PCR - This is the mainstay of diagnosis of SARS infection. A variety of specimens can be used including NPA (preferred), throat swabs, trachael aspirates, and faeces.

Virus Isolation - Vero E6 and FRhk4 cells may be used. However, the positivity rate is much lower than PCR and stringent Biosafety Level III facilities are required. Therefore, this is not recommended for small routine laboratories.

Serology - SARS virus infection may be confirmed by seroconversion or rising titres of antibodies. IFT and ELISAs are available but originally, whole virus antigen was used which required biosafety level III facilities. Because of the low predictive value of the first generation PCR assays, a serological diagnosis was often the only means of confirming a diagnosis of SARS.


A number of treatments were tried initially including ribavirin and steroids. However there is little evidence to suggest that any therapies used during this period was effective. In 2004, it was reported that researchers in China had successfully produced a vaccine that induced antibodies in 24 out of 36 volunteers but more research will be needed to ascertain whether it would be effective.

Post Epidemic

Since July 2003, laboratory acquired cases of SARS had been reported in Singapore, Taiwan and China. These have occurred in Biosafety level III and IV laboratories. Sloppy practices and procedures were to blame rather than failings in the containment equipment. In Jan 2004, a 32 old male with diagnosed with naturally acquired SARS in Guandong, China. He infection was linked to contact with civet cats and the Chinese authorities promptly ordered the slaughter of 10,000 civet cats and related species of animals in the area.


Respiratory Viruses Slide Set