Health SARS: An epidemic with a difference
The point to be taken on board is that the first infectious epidemic of the 21st century is not over. The outbreak has to be tackled by the international community jointly and actively with a great deal of transparency
By Dr Sabina Hussain,
Dr Azizullah Baig
Severe Acute Respiratory Syndrome has grabbed headlines and international attention in the last month. The WHO has reported more than 500 deaths from 27 countries all over the world. There are reports of probable cases from all but one continent, Antarctica!
SARS is the first multi country outbreak reported by WHO since 1996. It has spread across geographical boundaries from low and middle income countries to the developed world within a short timeframe, leaving an indelible mark on those afflicted in socio-economic terms. While the health organisations struggle to minimise the health and human cost incurred by this scourge of modern era, it is time to step back and take into account in which ways this disease differs from other infections.
The disease is believed to have started in China. While the world had attention focussed on the course of war against Iraq, the disease took into folds many more, setting a chain of transmission across international and geographic boundaries. This rapid spread indeed reflects some effects of globalization and increased air travel on the epidemiology of emerging infections in the modern times. Already 27 countries of the world are listed as affected by the World Health Organisation.
So far Pakistan has been blessed with no case report, although the neighbouring countries especially China and India as well have reported cases. The greatest toll has been in China where 21 out of the 31 provinces have confirmed cases and an additional four provinces have reported suspected cases. This is where the index case came from. Hong Kong and Singapore are the other countries to follow suit in terms of high number of SARS cases. With the 63 cases reported from Vietnam, the South East Asian bloc of countries has been amongst the worst hit regions of the world; the travel, trade and tourism to this region have taken a big blow. Taiwan has been the latest one to join the South East block of countries reporting SARS cases. It has reported a rapidly evolving epidemic with a 100 probable and 5 confirmed cases.
The magnitude of the problem in South East Asia and China in particular, makes it the need of the hour that Pakistan exercises utmost vigilance and surveillance of the situation.
The aetiology of Severe Acute Respiratory Syndrome seems to be viral. It is not yet established whether the corona virus isolated from the cases is associated causally or has a facilitative role in spread of infection. The association with human metapneumovirus is also possible. This has been isolated from isolates of 4 out of 5 cases in Canada. It is known that health and social practices are closely interlinked A Virologist John Oxford pointed out that if Guangdong is where SARS started, could the common practice there of keeping fowl and other domestic animals in the house be the key? There is a chance that the SARS virus, like H5N1 influenza, crossed species from chickens or animals to man. This fact is something to be borne in mind when planning public health measures to combat outbreak, particularly in rural areas.
The acute respiratory infection has been attributed to airborne transmission by the Centre of Disease Control; however the World Health Organisation has expressed scepticism about accepting this as the only mode of spread. The agent could be transmitted by droplets or by direct or indirect contact. The definitive route of spread and transmission is yet to be established. Faecooral transmission has not been excluded. The corona virus has been isolated from the stool samples of cases even after 2 -3 weeks after recovery.
According to WHO the incubation period is 3–10 days. Despite high rate of spread and infectivity and the need for intensive care for symptomatic support, the mortality due to disease itself has remained remarkably low. If there are no reported cases over a period of 20 days, this is considered to mark the end of the outbreak. The Director General of WHO expressed optimism about the worst being over when Vietnam was declared to be the first country to have contained the outbreak and Canada was to be excluded from the list of affected countries in the travel advisory issued by the WHO.
The diagnosis of SARS is based on the history of travel or contact with a case, flu like symptoms along with symptoms of upper and lowers respiratory infection and atypical early pneumonic changes on chest X-ray. The 3 laboratory based diagnostic tests viz. ELISA, PCR and Immunofluorescence test (IFA) are carried out on blood samples and oropharyngeal secretions. These have their own limitations as measures of disease control. The ELISA test detects antibodies after about 3 weeks of infection; the immunofluorescent assay is slow to give result as it requires the virus to grow in culture; the PCR molecular test gives many false negatives. A quick sensitive and specific test is subject to research in the 11 laboratories across the world which is working round the clock to develop effective measures to check the ‘near pandemic’. Thus the diagnosis of a probable case requires clinical suspicion and atypical X ray changes, obviating the need of expensive health care set up. What is mandatory of course is heightened awareness and education of the physician and health care workers particularly those working near the Pak- China Border and International airports.
The value of simple measures of infection control i.e. notification, isolation, contact tracing, quarantine and ongoing surveillance has begun to turn the tide over. The lessons from different courses taken by the epidemic in Vietnam and China highlight the importance of high level political commitment to disease containment and health protection.
The point to be taken on board is that the first infectious epidemic of the 21st century is not over. The outbreak in China and Hong Kong has to be tackled by the international community jointly and actively with a great deal of transparency. We live in a greatly interconnected and interrelated world. It is impossible to completely avert the knock off from economic consequence in one part of the world from another. So far the economic loss due to this disease is estimated to exceed 30 billion USD. Public health measures within international framework have to be adopted early on. It makes sense for Pakistan to join hands with the international community and the South East Asia in particular, to fight the spread of SARS. A step now will mean millions saved in terms of human and monetary costs - this is the simple lesson from the AIDS epidemic which is the only one to cross international boundaries on a large scale in the bygone century. This still rages to an extent that steps like reduction in cost of HIV drugs for the African countries seems a bit late to have a significant effect on the burden of disease.
Dr Sabina Hussain and Dr Azizullah Baig are faculty members at London School of Hygiene and Tropical Medicine, Department of Public Health &Policy.