Introduction
Severe acute respiratory syndrome (SARS) is a serious and potentially life-threatening viral infection that mostly affects the lungs. The infection is caused by the SARS coronavirus (SARS CoV).
There was an epidemic of SARS cases that lasted from 2002 to 2003. An epidemic is where a disease affects a significant amount of people at the same time.
Symptoms
The symptoms of SARS usually begin two to seven days after a person becomes infected. They include:
- high temperature (fever) of 38ºC (100.4ºF) or above
- fatigue (extreme tiredness)
- headaches
- chills
- muscle pain
- loss of appetite
- diarrhoea
Between three and seven days after the onset of these symptoms, the infection will begin to affect the respiratory system (the lungs and airways). This will cause additional symptoms, such as:
- a dry cough
- breathing difficulties
- an increasing lack of oxygen in the blood, which can be fatal in the most severe cases
The SARS epidemic
SARS originated in the Guangdong province of southern China in 2002. It is thought that a strain of the coronavirus usually only found in animals mutated (changed), enabling it to infect humans. See below for more information about mutations.
It is thought that the main sources of animal-to-human transmission were small weasel-like animals called civet cats, which are a popular delicacy in the region.
The SARS infection quickly spread from mainland China to other Asian countries. A small number of SARS cases also appeared in a number of other countries, including four in the UK. These were thought to have been caused by infected air travellers. There was also a significant outbreak of SARS in Toronto, Canada.
The SARS pandemic was eventually brought under control in July 2003, following a policy of isolating all suspected cases and screening all air passengers travelling from affected countries for signs of the infection.
During the period of infection, there were 8,096 cases of SARS and 774 deaths. This means that the virus killed about 1 in 10 people who were infected. People over 65 years old were particularly at risk. As many as 1 in 2 people in this age group died from the infection.
In 2004, there was another small SARS outbreak, which was linked to a medical laboratory in China. This outbreak was believed to have been caused by someone coming into direct contact with a sample of the virus, rather than through animal-to-human or human-to-human transmission.
This smaller outbreak of SARS was successfully contained and there have been no further outbreaks since.
How SARS is spread
SARS is an airborne virus, which means it is spread in a similar way to the common cold or influenza (flu).
The SARS virus is spread in small droplets of saliva that are coughed or sneezed into the air by an infected person. Infection can occur if the droplets are breathed in.
SARS can also be spread when someone with the virus touches surfaces, such as door handles, with unwashed hands. If you then touched the surface, you could also become infected.
It is thought that the SARS virus may also be spread through an infected person’s faeces (stools). For example, if they do not wash their hands properly after going to toilet, they may be able to pass on the infection to others.
Evidence from the 2002-2003 SARS epidemic showed that people who were living with (or caring for) someone with a known SARS infection were most at risk of developing the infection themselves.
Treatment
There is currently no cure for SARS, but research to find a vaccine is ongoing. Currently, treatment for the condition is largely supportive – for example, using ventilators to assist with breathing.
Due to the contagious nature of SARS, anyone who is thought to have the condition will need to be isolated in a secure hospital ward until their symptoms have passed, and tests show that they are free from infection.
Mutation of SARS virus
Like all living things, a virus is constantly changing and evolving. Mutations occur when some of the genetic information that is stored inside an organism changes.
Mutations occur randomly, and most are not particularly significant. However, a mutation sometimes changes the outer surface proteins of a virus. These proteins determine which cells of which species a virus is able to infect. By rare chance, the mutated virus may develop the ability to infect humans.
Many worldwide epidemics (pandemics) that have occurred in recent history are thought to have been caused by a virus found in animals, which was previously incapable of infecting humans, but then mutated and became capable of infecting humans.
Examples of this include:
- SARS
- HIV – thought to be a mutated version of a virus found in monkeys
- avian flu – a mutated version of a flu virus found in birds
- swine flu – a mutated version of a flu virus thought to have originated in pigs
What will happen if SARS returns?
Although the threat of SARS to public health seems to have passed, international health officials still remain alert. The World Health Organisation (WHO) monitors countries throughout the world for any unusual disease activity.
Therefore, if another SARS outbreak were to occur, it should be possible to limit the spread of infection by using the same measures implemented during the 2002-3 pandemic (see above) and perhaps by developing a vaccine.
^^ Back to top