Severe Acute Respiratory Syndrome (SARS)
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Severe Acute Respiratory Syndrome is caused by a coronavirus called SARS CoV. The disease may have started in pigs or ducks in rural south China and mutated to affect humans.
It seems that both abnormal immune responses and injury to immune cells may be key factors in the pathogenesis of this new disease.
SARS should not be confused with another zoonosis from the same area called avian flu
Epidemiology
The Severe Acute Respiratory Syndrome (SARS) was first recognised in March 2003 but probably had its origins in the Guangdong Province of China in November 2002. Between March and July 2003, over 8,000 probable cases of SARS were reported from around 30 countries. The 2002-2003 SARS outbreak affected mostly China, Hong Kong, Singapore, and Taiwan. Canada had a significant outbreak around Toronto. Since April 2005, SARS seems to have been contained worldwide.
Clinical Suspicion
History
Examination
Investigations
Laboratory diagnosis of SARS depends upon any one of the following:
For microbiology:
For other tests they recommend:
Management
After discharge from hospital:
Prevention of Spread
Prognosis
The death rate is much higher than with influenza. Between November 2002 and July 2003 there were 8,098 cases reported worldwide of whom 774 died (9.6%) and 7,324 recovered.
Outcome of SARS
China # of cases 5327, # of deaths 349, mortality rate 6.5%
Hong Kong # of cases 1755, # of deaths 299, mortality rate 17%
Taiwan # of cases 367, # of deaths 37, mortality rate 10.7%
Canada # of cases 251, # of deaths 43, mortality rates 17%
These figures suggest that, despite the need for high technology, the death rate appears lowest in China. Figures for various clinical parameters from Taiwan, Canada and Hong Kong were remarkably similar. However, government statistics from China are greeted with a degree of scepticism. Risk factors for severe disease were diarrhoea, high peak LDH and CRP, high AST and creatine kinase on admission and also peak values.
Mortality increases with age. Chronic illness and immune suppression are likely to increase mortality. So does diabetes. WHO has declared that if no new cases of SARS are reported in an area for 20 days, infection in that area is said to be contained.
A study from the New Territories of Hong Kong concluded that there is little evidence of widespread subclinical or mild forms of SARS coronavirus infection. Clinical diagnoses during the outbreak were reasonable and resulted in appropriate triaging.
Prevention
There is not yet any effective vaccine although production looks promising. Effective prevention lies in early detection of an outbreak and adequate containment.
Statistical and reference material was gained from patient.co.uk
Clinic telephone +86 (0574) 86000000 (Mon-Fri closed)
Website designed and maintained by Foreigners Medical Clinic, Ningbo Development Zone Central Hospital
All content on this website in its entirety is subject to copyright. No part is to be copied without express written permission of Ningbo Development Zone Central Hospital 宁波开发区中心医院
Severe Acute Respiratory Syndrome is caused by a coronavirus called SARS CoV. The disease may have started in pigs or ducks in rural south China and mutated to affect humans.
It seems that both abnormal immune responses and injury to immune cells may be key factors in the pathogenesis of this new disease.
SARS should not be confused with another zoonosis from the same area called avian flu
Epidemiology
The Severe Acute Respiratory Syndrome (SARS) was first recognised in March 2003 but probably had its origins in the Guangdong Province of China in November 2002. Between March and July 2003, over 8,000 probable cases of SARS were reported from around 30 countries. The 2002-2003 SARS outbreak affected mostly China, Hong Kong, Singapore, and Taiwan. Canada had a significant outbreak around Toronto. Since April 2005, SARS seems to have been contained worldwide.
- Most cases of SARS appear to have been transmitted from close contact with infected patients. In May 2003, WHO reported that only 16 of the more than 7,800 people infected with the virus had contracted it on aeroplanes. After airlines began screening passengers for symptoms, especially fever no further cases from air travel were reported.
- There is no difference in susceptibility to infection with regard to age, sex or race.
- Where percentages are given below they will be based mainly on papers giving experience of 144 patients from Toronto, 29 from Taiwan and 138 from Hong Kong. Figures from the all centres tend to be fairly similar.
- Another paper from Toronto also looked at those who required admission to the intensive care unit.
Clinical Suspicion
- SARS is not usually suspected unless the person is known to have come from an area where he has been exposed.
- The commonest mode of transmission is droplet spread.
- Healthcare workers and the families or carers of those who have been infected are at greatest risk. In the Toronto study, 77% (111/144) were exposed within a hospital setting. 164 healthcare workers were quarantined, closing 73 ICU beds and 16 workers (10%) developed SARS. In their study of 196 patients, 38(19%) became critically ill of whom 7 (18%) were healthcare workers. In Hong Kong half of 138 patients were healthcare workers.
- Close contact permits spread. Close contact means kissing, embracing, sharing eating or drinking utensils, conversation less than a metre apart or physical examination of the person. It does not include walking past someone or sitting across a waiting room or office for a brief period.
- Faeco-oral spread from diarrhoea may be possible.
- Visiting an infected or suspected area, including an airport, within the last 10 days raises suspicion.
- Incubation period is usually 2 to 7 days but may be up to 10 days and 14 days has been reported.
History
- The 1st stage is a flu-like prodrome with fever reported in 99 to 100%, fatigue, headache, chills in 62% and 73%, aching muscles in 69% and 61%, malaise, anorexia, and sometimes diarrhoea. This phase lasts 3 to 7 days.
- The 2nd stage affects the lower respiratory tract and begins 3 days or more after incubation. There is a dry non-productive cough in 69%, dyspnoea and possibly progressive hypoxia. The cough varies from mild to severe and is usually unproductive. Dyspnoea was reported in 42% and 41%.
Examination
- Temperature is usually over 38°C but antipyretics may bring this down. In Toronto fever was reported in 99% but found in only 85%.
- Moderate respiratory disease is diagnosed with pyrexia and at least one respiratory feature of cough, dyspnoea, breathing difficulties or hypoxia.
- Severe disease is diagnosed with the above plus pneumonia or respiratory distress syndrome.
- Examination of the chest is often remarkably normal.
- Rhinorrhoea was found in only 2%.
Investigations
- Pulse oximetry and blood gases should be monitored as oxygen and even ventilation may be required.
- FBC shows a modest lymphopenia in 54%, 72% and 70%, leukopenia, and thrombocytopenia in 35% and 45%.
- U&E show mild hyponatraemia and hypokalaemia. Hypocalcaemia was found in 60%
- Enzymes show elevated lactate dehydrogenase in 87%, 62% and 71%, alanine aminotransferase, hepatic transaminase and creatine kinase levels in 32%.
- Chest X-Ray may be normal at first and it may take a week or more to become abnormal but by 10 to 14 days all are abnormal. However, in Taiwan all CXR were abnormal at presentation and 69% became worse. Focal interstitial infiltrates can occur early and may progress to a more patchy, general distribution. At first a peripheral opacity near the pleura may be the only abnormality. High-resolution CT (HRCT) of the chest may show infiltration behind the heart. With progression opacities become more widespread. The lower lung fields are affected first. Calcification, cavitation, pleural effusion or lymphadenopathy does not occur. HRCT may be useful where there is strong suspicion of the disease but CXR appears normal.
Laboratory diagnosis of SARS depends upon any one of the following:
- Antibodies to SARS-CoV in specimens obtained during the acute illness or more than 28 days after the onset of the illness.
- Detection of SARS-CoV RNA by reverse transcriptase-polymerase chain reaction (RT-PCR) and confirmed with a second PCR assay using a second aliquot of the specimen.
- Culture of the virus.
For microbiology:
- Expectorated sputum (if available)
- Urine (20-30ml)
- Stool
- EDTA blood (20ml for PCR)
- Acute serology (20ml of clotted blood)
- Do not obtain a nasopharyngeal aspirate as this is likely to generate aerosols.
For other tests they recommend:
- Chest x-ray
- Pulse oximetry
- Blood gases if oxygen saturation <92% on air
- Full blood count, urea, creatinine, electrolytes, liver function tests, lactate dehydrogenase, creatine kinase and C-reactive protein.
- Other samples for diagnostic testing as appropriate (remember there are much commoner causes of community acquired pneumonia than SARS).
Management
- Isolation is required. Contacts should be isolated at home. The ill patient in hospital requires stringent barrier procedures.
- Pulmonary function and blood gases should be monitored as ventilation may be required. In the Taiwan study, 31% required ventilation although a study from Canada suggested up to 20%.7 A different Canadian study supported this with 38/196 becoming critically ill of whom 29 required ventilation. This represents 76% of the critically ill and 15% overall.
- As it is a viral infection, antibiotics are of no benefit unless there is nosocomial infection.
- If the patient requires ventilation, intravenous co-amoxiclav 1.2g tds or cefuroxime 1.5g tds plus erythromycin 500 mg qds or clarithromycin 500mg bd are recommended. Try to avoid high flow rates of oxygen as this facilitates droplet spread.
- Pulse steroids were used in Taiwan with improvement in 14 of 17.
- Antiviral agents may help. Ribavarin was used in 88% in Canada. It caused haemolysis in 76% with a fall in Hb of 2g/dL in 49% whilst benefit was dubious. Its use is not recommended.
- Interferon beta seems promising and is recommended.
After discharge from hospital:
- Patients should monitor and record their temperature twice daily. If they have an elevated temperature of 38° or above on two consecutive occasions they should inform (by telephone) the health care facility from which they were discharged.
- Patients should remain at home for 7 days after discharge, keeping contact with others at a minimum. This is to reduce the risk of transmission until more is known regarding the potential for continued carriage in convalescent cases.
- Additional home confinement may need to be considered, particularly in patients who are immunosuppressed. Inform the local Health Protection Team regarding the hospital discharge of patients to ensure follow-up in the community.
- Convalescent serology should be obtained at 21 days after the date of onset of the disease.
Prevention of Spread
- The relevant agencies for communicable diseases must be notified.
- Contact tracing should be performed. Travel restrictions may be implemented or screening air travellers for pyrexia. Scanners can detect temperatures above 37.5°C but false positives are common from sunburn, alcohol consumption and other causes.
- Patients in home or hospital should be kept away from others as much as possible until 10 days after the resolution of fever.
- Members of the household should wash their hands frequently with an alcohol based solution.
- Disposable gloves should be used when handling body fluids.
- The patient should wear a mask or at least cover the mouth when coughing.
- Eating utensils, towels and bedding should not be shared.
Prognosis
The death rate is much higher than with influenza. Between November 2002 and July 2003 there were 8,098 cases reported worldwide of whom 774 died (9.6%) and 7,324 recovered.
Outcome of SARS
China # of cases 5327, # of deaths 349, mortality rate 6.5%
Hong Kong # of cases 1755, # of deaths 299, mortality rate 17%
Taiwan # of cases 367, # of deaths 37, mortality rate 10.7%
Canada # of cases 251, # of deaths 43, mortality rates 17%
These figures suggest that, despite the need for high technology, the death rate appears lowest in China. Figures for various clinical parameters from Taiwan, Canada and Hong Kong were remarkably similar. However, government statistics from China are greeted with a degree of scepticism. Risk factors for severe disease were diarrhoea, high peak LDH and CRP, high AST and creatine kinase on admission and also peak values.
Mortality increases with age. Chronic illness and immune suppression are likely to increase mortality. So does diabetes. WHO has declared that if no new cases of SARS are reported in an area for 20 days, infection in that area is said to be contained.
A study from the New Territories of Hong Kong concluded that there is little evidence of widespread subclinical or mild forms of SARS coronavirus infection. Clinical diagnoses during the outbreak were reasonable and resulted in appropriate triaging.
Prevention
There is not yet any effective vaccine although production looks promising. Effective prevention lies in early detection of an outbreak and adequate containment.
Statistical and reference material was gained from patient.co.uk
Clinic telephone +86 (0574) 86000000 (Mon-Fri closed)
Website designed and maintained by Foreigners Medical Clinic, Ningbo Development Zone Central Hospital
All content on this website in its entirety is subject to copyright. No part is to be copied without express written permission of Ningbo Development Zone Central Hospital 宁波开发区中心医院