What you should know about 'mystery killer bug'
evere acute respiratory syndrome (SARS) is an emerging illness that has so far claimed 10 lives and infected some 300 people across 13 countries. It has attracted considerable media attention in the UK since the outbreak was first recognised at the end of February.
What is the cause?
SARS exhibits many of the features of an infectious disease: no pathogen has yet been identified but suspicion is focusing on a paramyxovirus-like virus. The paramyxovirus family includes measles, mumps and the parainfluenza viruses. Initial concerns were that SARS might be due to a variant of influenza that could cause a pandemic, but to date there is no evidence to support this.
Currently SARS is a diagnosis of exclusion. Whenever a known cause is found that will fully account for a patient's clinical condition, they should no longer be considered to be a case of SARS. This occurred with a possible SARS case in the UK which was subsequently diagnosed as influenza A.
How does SARS present clinically?
Main symptoms are a pyrexial illness (>38°C) with a dry cough, shortness of breath or breathing difficulties. Chest X-rays changes indicative of pneumonia also occur. SARS may be associated with headaches, muscular stiffness, loss of appetite, malaise, confusion, rash and diarrhoea.
In the prodrome/early stages the clinical features are similar to many other conditions including influenza. Almost certainly the cases reported so far represent the more severe end of the disease spectrum and many more mild/asymptomatic cases have probably occurred and will continue to do so.
How is it spread?
Based on currently available evidence, SARS is believed to spread through respiratory (and possibly other body) secretions, Close contact with an infected person is needed for the infective agent to spread.
Most cases since the beginning of the outbreak were in hospital workers who had cared for SARS patients and patients' immediate family members. Close rather than casual contact would therefore appear to be necessary for spread. In seven countries where imported cases were reported there has been no documented local transmission so far (see box on page 44).
Which individuals are at particular risk?
If SARS is caused by paramyxoviruses, then experience with this group of viruses would suggest the very young, elderly, with chronic lung or heart disease, and those who are immunocompromised, may experience more severe disease.
What is the incubation period?
The incubation period is believed to be short, between two and seven days with three to five days being most common. However, speed of international travel creates a risk that cases can rapidly spread around the world.
How infectious is SARS?
From the limited epidemiological data available and assuming that this illness has a viral aetiology, SARS appears to be less infectious than influenza.
When can an infected person transmit it?
person transmit it?
SARS is spread during the acute phase. Whether it is also spread before the onset of symptoms and after their resolution is not known.
What is the source of SARS?
If SARS has a viral aetiology then the reservoir/host may be either human or zoonotic.
How should GPs manage a patient?
GPs may see cases that fulfil the case criteria (see disease features). The Public Health Laboratory Service has issued this advice:
'GPs should make an initial assessment as to clinical severity. If it is considered that the case requires hospital referral on clinical grounds, then this should be dealt with through normal channels, but alerting the receiving physicians to the travel history.
'If it is considered that the illness is mild/ resolving/does not require hospitalisation, you should ensure an acute and a convalescent (14 days later) serum sample (20ml in a plain glass tube) are taken, together with 20ml urine specimen (MSU, CSU or clean catch collection) in a sterile container and sent to your local laboratory with a clear indication of the suspected illness (SARS) and travel history. All cases notified to public health authorities/ laboratory microbiologists should have an acute and convalescent blood sample, even with a very mild illness.'
Are treatments available?
While some medicines have been tried, no drug can, at this time, be recommended for prophylaxis or treatment. Antibiotics appear to be ineffective. Symptoms should be treated by adequately protected health professionals.
Current World Health Organisation advice recommends no travel restrictions.
All travellers should be aware of the main symptoms and signs of SARS. People who have these symptoms and who have been in close contact with a person diagnosed with SARS, or have a recent history of travel to areas where cases of SARS have been spreading, should seek medical attention and inform health care staff of recent travel. Travellers who develop these symptoms are advised not to undertake further travel until fully recovered.
The PHLS recommends that clinicians should be alert for persons with onset of illness after February 1, 2003, with:
· Fever >38°C/100.4°F and
· One or more signs or symptoms of respiratory illness including cough, shortness of breath, difficulty in breathing, hypoxia, radiographic findings of pneumonia, or respiratory distress and one or more of the following:
· History of travel to Hong Kong or Guangdong Province in China or Hanoi, Vietnam, within seven days of symptom onset
· Close contact with people with respiratory illness and with the above travel history (close contact includes having cared for, lived with, or had direct contact with respiratory secretions and body fluids of a person with the syndrome).
Who should you notify?
Contact your local health protection
unit or consultant in communicable diseases control as soon as is reasonably possible.
Knowledge about a case will assist both prevention of secondary spread and provide further information about the natural history of SARS.
SARS: cumulative cases (reported, probable and suspect)
Country Cumulative Numbers Local
number of cases* of deaths transmission**
Germany 4 0 None
Canada 11 3 Yes
Singapore 65 0 Yes
Hong Kong 260 10 Yes
Special Administrative Region of China
Taiwan, China 6 0 Yes
Thailand 5 0 None
Vietnam 58 4 Yes
Spain 1 0 To be determined
Switzerland 2 0 To be determined
United Kingdom 3 0 To be determined
USA*** 37 0 To be determined
France 1 0 None
Italy 2 0 None
Republic of Ireland 1 0 None
Data source: www.who.int/csr/sarscountry/2003_03_20/en/ accessed March 20
*This figure includes the numbers of deaths
**Evidence of secondary transmission in the country: presence of affected areas
***Includes suspect cases under investigation
****Suspect and probable cases have been reported in Guangdong province, China
figures are being updated