Chapter 5: SARS: lessons from a new disease
Detection and response
On 15 March 2003, when the second alert was made, the cause of SARS had not yet been identified. Cases were concentrated in hospital workers and did not respond to medicines known to be effective against a number of different lung infections. Many patients were rapidly progressing to severe pneumonia. The situation was alarming: no patients, including young and previously healthy health workers, had recovered. Many of the patients were in a critical condition, several required mechanical ventilatory support, and two had died. The spread to major cities around the world meant that any city with an international airport was at potential risk of imported cases. From the outset, WHO's objective was clear: to halt further international spread and interrupt human-to-human transmission through a global containment effort, and by so doing to minimize opportunities for the disease to establish endemicity (see Box 5.1).
Box 5.1 The response to SARS in the Western Pacific Region
More than 95% of SARS cases occurred in the Western Pacific Region. As an immediate response, a SARS outbreak response and preparedness team -- including international experts -- was established in the Regional Office. The main objectives were to:
- contain and control the outbreaks;
- support the health care infrastructure in affected countries;
- provide guidance and assistance to enable vulnerable countries to prepare for the possible arrival of the virus;
- provide the most up-to-date information to health officials and respond to public concerns.
Teams of epidemiologists and infection control experts were immediately sent to China, including Hong Kong Special Administrative Region, as well as to the Philippines, Singapore and Viet Nam and across the southern Pacific, training health care workers in infection control procedures and preparing them for the possible arrival of the disease. Practical infection control and preparedness guidelines and training tools were developed, and the first version of preparedness guidelines was issued at the beginning of April. Logistic support and supplies (personal protective equipment, including masks, collection materials for blood and respiratory samples, and internationally approved containers for shipment of samples) were sent to both affected and unaffected countries, supported by a US$ 3 million grant from the Government of Japan.
Countries were classified according to three levels of risk and three levels of capability to respond to SARS cases, in order for WHO to prioritize its support to countries. WHO worked closely with countries to ensure that enhanced surveillance was put in place to enable early detection of cases and contact tracing. Guidelines were drawn up on enhanced surveillance, hospital and community infection control, international travel, laboratory procedures and public awareness. To improve public awareness, close contact was established with national media focal points, and the web site of the Western Pacific Regional Office was regularly updated.
A regional laboratory network was established to ensure that necessary testing for SARS could be done for countries with limited laboratory capacities. National and regional reference laboratories were identified and shipping of specimens was arranged between the laboratories.
WHO's efforts were paralleled by the contribution of Member States. Viet Nam was the first to interrupt local transmission of the virus. Other countries introduced a wide range of measures, including isolation, home quarantine and comprehensive contact tracing. The willingness of governments in the Western Pacific Region to put public health considerations ahead of economic concerns about the impact of SARS was crucial to the success of the collaborative effort.
The global response to SARS was in reality the roll out of a way of detecting and responding to outbreaks that had been developed over the preceding seven years by WHO and its partners, partly as a result of major weaknesses that came to light during the 1995 Ebola outbreak in the Democratic Republic of the Congo and during previous outbreaks of plague in India and cholera in Latin America. The SARS response depended on collaboration of the world's top public health and laboratory experts, and took advantage of up-to-date communication technologies, including the Internet and video and telephone conferencing.
Two principal partners of the WHO Global Outbreak Alert and Response Network (GOARN), an electronically interconnected network of experts and institutes formally set up in early 2000, contributed to the detection of the SARS outbreak. One was the Canadian Global Public Health Intelligence Network (GPHIN), a worldwide web-crawling computer application, used by WHO since 1997, that systematically searches for keywords in seven different languages to identify reports of what could be disease outbreaks. Throughout the outbreak, GPHIN provided the raw intelligence that helped WHO maintain up-to-date and high-quality information on indications that the disease might be spreading to new areas. The second partner was the WHO Influenza Laboratory Network of 110 laboratories in 84 countries that constantly keeps the world in general and vaccine manufacturers in particular informed of which strains of influenza are circulating, so that an effective influenza vaccine can be produced each year.
On 10 February 2003, GPHIN and other partners of GOARN identified reports of an outbreak associated with health worker mortality and the closing of hospitals in Guangdong. One day later the Chinese government officially reported to WHO an outbreak of respiratory illness, beginning in mid-November, involving 300 cases and five deaths in Guangdong Province. Just over a week later, on 19 February, an outbreak of avian influenza was reported to the WHO Influenza Laboratory Network by the collaborating laboratory in Hong Kong. This outbreak first came to light when a 33-year-old man died of an unknown cause after returning from a family trip to Fujian Province, China. His 8-year-old daughter had died of a similar disease while in Fujian Province and his 9-year-old son was hospitalized in Hong Kong with the same symptoms. It was from this son that avian influenza virus was isolated and reported to the Influenza Laboratory Network. The same influenza virus had been identified in Hong Kong in 1997. Control efforts at that time required the slaughter and incineration of all chickens in the many live markets there; human-to-human transmission was never established.
This heightened level of alert led to the identification of an early SARS case in Viet Nam on 28 February 2003. At the same time as GOARN collected information about this outbreak in real time, it sent an international team of partners to work with the Viet Nam authorities to better understand the disease, and by 12 March GOARN had accumulated the initial information necessary to issue the first global alert. It was through the continued instant sharing of information by governments, public health experts, clinicians and laboratory scientists that evidence-based decisions could progressively be made, culminating in the successful containment of SARS.
Under GOARN, a virtual collaborative network of 11 leading laboratories, linked by a secure web site and daily teleconferences, identified the SARS causative agent and developed early diagnostic tests. The network, in turn, served as a model for similar electronically linked groups of clinical and epidemiological experts who pooled clinical knowledge and compiled the epidemiological data needed to chart the outbreak's evolution and assess the effectiveness of control interventions.
WHO issued daily updates about the outbreaks on its web site to keep the general public -- especially travellers -- informed and, as far as possible, to counter rumours with reliable information. Equally important, the web site was used to issue a range of evidence-based technical and practical guidelines for control as knowledge and information about the disease progressed and became available through the virtual groups of experts.
As more and more evidence accumulated through real time collaboration of public health experts, a range of additional evidence-based control measures became possible. It was soon evident, for example, that people with SARS continued to travel internationally by air after 15 March, and that some of them had infected passengers sitting nearby. At the same time it was also apparent that contacts of SARS patients likewise continued to travel, becoming ill once they arrived at their destination. Recommendations were therefore made that countries with major outbreaks should screen departing passengers to make sure that they did not have fever and other signs of SARS, or known contact with SARS patients.
As the outbreak continued in Hong Kong, contact tracing there further demonstrated that transmission of SARS was occurring outside the confined environment of the health care setting, and later suggested that it was also occurring following exposure to some factor in the environment, thus creating further opportunities for exposure in the general population. Additional evidence-based guidance was therefore made for sites where contact tracing could not link all cases to a chain of transmission, on the understanding that if the disease were spreading in the wider community it would greatly increase the risk to travellers and the likelihood that cases would be exported to other countries. This guidance was aimed at international travellers, and recommended that they postpone all but essential travel to designated areas in order to minimize their risk of becoming infected. Such guidance was also needed in view of the confusion created by several different national recommendations, many of which were based on criteria other than epidemiological data.
Authorities in areas where outbreaks were occurring responded to SARS with mass public education campaigns and encouraged populations to conduct daily fever checks. Hotlines and web sites answered questions. Screening measures were set up at international airports and border crossings, and procedures of infection control were reinforced in hospitals. Singapore drew on its military forces to conduct contact tracing, while Hong Kong adapted a tracing system that had been developed for use in criminal investigations and electronically mapped the location of all residences of cases. Chinese authorities opened hundreds of fever clinics throughout the country where suspected SARS cases were triaged. Heads of state and ministers of health of of countries of the Association of Southeast Asian Nations (ASEAN) and the Asia--Pacific Economic Cooperation (APEC) met and resolved to establish closer collaborative mechanisms for disease surveillance and response. Health staff everywhere worked with dedication, and many, including WHO staff member Dr Carlo Urbani, lost their lives.
On 5 July 2003, WHO announced that Taiwan, China, where the last known probable case of SARS had been isolated 20 days earlier, had broken the chains of human-to-human transmission. A recurrence of SARS cannot, however, be ruled out. Further research on many unresolved questions is needed. In the meantime, systems are now in place to detect a re-emergence should it occur (4).