The Global Response

As noted earlier, the WHO response to SARS was spearheaded by GOARN. To extend its capacity for surveillance, reporting, and containment, WHO enlisted the support of public health services from the United States, United Kingdom, Germany, France, and other nations. GOARN recruited more than 60 teams of medical experts to assist with infection control in SARS-affected areas, which included 84 personnel from the U.S. CDC. Ultimately, more than 800 CDC employees were involved in the response to SARS.

Through GOARN, WHO also established a virtual network of 11 leading infectious disease laboratories in 9 countries. Connected by a secure website and daily teleconferences, the laboratories collaborated to identify the causative agent of SARS and to develop a diagnostic test; similar groups were also created to pool clinical knowledge and compare epidemiological data on SARS. By April 16, exactly 1 month after the laboratory network was established, its researchers had conclusively identified SCoV as the causative agent.

When evidence revealed that persons infected with SCoV continued to travel—placing adjacent passengers on airplanes at risk of infection—WHO advised airlines to screen departing passengers (WHO, 2003n). Further WHO advisories to avoid all but essential travel to certain high-risk areas were the most restrictive in the history of the organization (WHO, 2003c). The U.S. CDC and Health Canada also issued advisories that warned against travel to SARS-affected countries.

Chinese Cooperation

Members of a GOARN mission to China in late March warned that country’s health authorities that if SARS was not brought under control in China, there would be no chance of controlling the global threat of SARS. Within days, the GOARN team announced that Chinese authorities had agreed to join the GOARN collaborative effort to contain the outbreak and prevent further international spread (WHO, 2003i).

At a March 28 meeting with the Chinese Minister of Health, WHO officials determined that the atypical pneumonia in Guangdong was SARS and that the first cases had appeared in mid-November 2002 (WHO, 2003c). Data provided by the Chinese Center for Disease Control suggested an association between exotic food animals and SARS, indicating the possibility of a zoonosis. More than a third of the earliest SARS cases—those that emerged in China before February 2003—occurred among workers who handled, butchered, or sold wild animals in Guangdong’s markets, or who prepared and served them as food. Viruses closely resembling SCoV were eventually isolated from several animal species sold in such markets; however, a natural reservoir for SCoV has yet to be found (Guan et al., 2003).

Although Chinese officials acknowledged that SARS had emerged in their country, they continued to downplay the extent and severity of the outbreak. This led the WHO team in Beijing to take the unusual measure of publicly expressing “strong concern over inadequate reporting” of SARS cases on April 16 (WHO, 2003c).

On April 20, national government leaders declared a “nationwide war on SARS” and removed the mayor of Beijing and the Minister of Health from their posts reportedly for failing to satisfactorily address the epidemic (WHO, 2003c). Thereafter, China increased both its disease control efforts and its cooperation with the international community in the effort to contain SARS. Both the Chinese government and the public took considerable action to halt the epidemic. A workshop participant described how large numbers of government offices, schools, and universities were shut down. Quarantines to prevent public gatherings and travel from cities were imposed to prevent the spread of the disease to the rural interior of the country, where it was feared that medical resources would be unable to contain or treat the disease. In late June, after more than 5,000 cases had been reported, the disease was contained in China. By this time, Beijing had reported 348 deaths and Hong Kong, 298—the two greatest death tolls due to SARS for any city or region at that time (WHO, 2003c).

When WHO declared on July 5 that all chains of SARS transmission had been broken, the disease was thought to have spread to more than 30 countries, only 8 of which—Canada, China, Hong Kong, the Philippines, Singapore, Taiwan, the United States, and Vietnam—reported more than 10 probable cases.

Assessing the Use of Public Health Tools

The experience of the SARS outbreak and the history of its control hold clues to the origin and spread of the disease—knowledge that will help to prevent or curtail its resurgence. In assessing the public health response to SARS at both the global and local levels, workshop participants focused on the roles of surveillance and containment in limiting the spread of SARS and anticipated the use of these tools against future microbial threats.

Surveillance

Broad international networks of individuals and organizations within and across disciplines were responsible in large part for the successful surveillance of the SARS epidemic. Electronic communication networks such as the Global Public Health Information Network (GPHIN) and ProMED mail reported the early outbreaks. ProMED uses electronic communications to provide up-to-date news on disease outbreaks and is open to all Internet users. GPHIN, established by Health Canada in collaboration with WHO, is an Internet-based application that continuously scans global electronic media (news wires, websites) for information on global public health risks, including infectious disease outbreaks. Although these systems ultimately proved to be critical tools for effective surveillance, workshop participants questioned the ability of the existing system to rapidly identify novel emerging threats, which induce symptoms and behaviors characteristic of other infectious diseases that may not initially promote concern or further investigation. Additionally, the sensitivity of the system was considered inadequate because of its inability to correlate disparate data from multiple surveillance networks that, only when taken as a whole, might surpass a threshold that signals an alarm to public health professionals. Retrospective analyses of the reports on several surveillance networks revealed multiple reports of atypical pneumonia in China between November 2002 and January 2003. However, the lack of collaborative data analysis between multiple reporting systems and the initial absence of clustering allowed the virus to spread unchecked. GOARN identified and verified subsequent outbreaks with the help of the media, nongovernmental organizations, agencies of the United Nations, and public health teams from many countries in addition to those where the outbreaks occurred. GOARN communicated new information to authorities and the public through the WHO website, satellite broadcasts, and news conferences.

The SARS epidemic became a front-page event for the worldwide news media. Daily updates posted on the WHO website for travelers and the public sought to counter rumors with reliable information. The U.S. CDC, which spear-headed the U.S. response to SARS, provided information through its website, satellite broadcasts, and a public response hotline for clinicians and the public.

The vast Emerging Infections Network created by the Asian Pacific Economic Community (APEC) also conducted surveillance for SARS. In addition, it provided an arena for discussions relevant to both biomedical research and disease control, and it monitored the economic impact of SARS in its member countries, which comprise 2.5 billion people and conduct nearly half of the world’s trade (see Kimball et al. in Chapter 5).

Containment

While many aspects of the public health response to SARS benefited from such technological developments as global broadband telecommunications, the containment of the epidemic ultimately depended on the venerable strategies of identifying and isolating persons who fit the case definition and tracing and quarantining their contacts. In countries such as Vietnam and Singapore, where these measures were imposed soon after the identification of index cases, the chain of infection was broken quickly. By contrast, China’s delayed response to the epidemic rendered contact tracing impossible and resulted in the need for broader quarantines.

The U.S. strategy to prevent an outbreak within its borders focused on the early detection of symptom onset and rapid implementation of infection control and isolation. Only in high-risk settings such as health care facilities or airline flights carrying passengers exposed to SARS-infected individuals did CDC suggest the use of quarantine (by definition, the isolation of asymptomatic individuals believed to have been exposed to a contagion). In the absence of an outbreak, the agency directed its efforts toward informing the traveling public about high-risk areas, issuing travel advisories, distributing millions of health alert notices in seven languages at airports and U.S.–Canada border crossings, and responding to symptomatic incoming passengers. However, several other countries quarantined travelers arriving from SARS-affected areas.

The relative effectiveness of various strategies applied to SARS containment— the use of standardized case definitions and laboratory testing to identify the infected, the isolation of ill persons, and the quarantine of contacts—remains to be determined. Based on the present understanding that asymptomatic infected individuals transmit SARS at a low rate, if at all (WHO, 2003j), and that transmission occurs primarily through contact with ill individuals, workshop participants suggested that quarantine of contacts was the least effective of these strategies. However, they also recognized that quarantine could facilitate the containment of a SARS-like disease by reducing the number of contacts by infected individuals during the delay between the onset of symptoms and diagnosis. This would be particularly effective when, as in the case of SARS, symptoms are nondescript and difficult to distinguish from those of other illnesses. It was also emphasized that quarantine should not be viewed as an impermeable cordon sanitaire confining those at risk for illness with the known ill, but as a scalable, self-protective measure that can be adapted to local conditions.

Less problematic than quarantine, the isolation of infected individuals clearly played a central role in containing SARS. Although isolating SARS patients within hospitals could be viewed as increasing the risk of infection for health care workers and other hospital staff, evidence from Toronto indicates that hospital personnel can be protected through strict infection-control practices, such as washing hands, wearing masks and gloves, and requiring patients to wear masks. The most effective type of mask remains to be determined, however.

Finally, even if it were known which of the various strategies used to contain SARS were most effective, it is far from certain whether they would continue to be effective should SARS return. For example, although it appears that quarantine helped control SARS in China and Toronto, it did so largely because of the limited contagiousness of the virus. The likelihood that SCoV could become more easily transmissible cannot be determined without a better understanding of its biology, ecology, and natural history—knowledge that will be essential to mounting a rational response should SARS recur (see Cetron et al. in Chapter 1).

Evaluating SARS Containment Measures

To plan rationally for the containment of a future SARS outbreak, it will be important to know the relative effectiveness of the various measures taken to contain the recent epidemic. In the absence of such information, the strategy for containing SARS should emphasize overall preparedness at the local level in every community and hospital, participants agreed.

Participants discussed techniques and equipment to protect frontline caregivers of SARS patients in the hospital and at home. Simple habits such as frequent handwashing with soap and water are very important to prevent the transmission of any infectious agent. Other measures include wearing a mask that covers the nose and mouth, protective eyewear, gloves, gowns, or a containment suit. Participants noted that masks are effective only if they fit snugly and are not removed when the wearer coughs.

During the discussion of masks, participants debated the relative protectiveness of standard surgical masks compared with N-95 masks (so named because 95 percent of the time, they filter out any particle equal to or greater than 0.3 microns in size). Coronaviruses are smaller than 0.3 microns, so N-95 masks would not capture them; however, because viruses may travel in clumps, N-95 masks theoretically could capture some of the agent (University of California–Berkeley, 2003). Participants discussed a case control study in five Hong Kong hospitals in which wearers of surgical masks and N-95 masks did not contract the SARS coronavirus, while a few wearers of paper masks became infected (Seto et al., 2003). A larger study to validate this finding was proposed.

One workshop presentation described a relatively inexpensive mobile technology that potentially could be used to isolate individual patients during transport to and within hospitals, to protect staff during high-risk procedures such as intubation or bronchoscopy, to decontaminate large areas such as hospital waiting rooms or airplanes, and to create air exchange systems for isolation facilities or areas within hospitals (see Schentag et al. in Chapter 4). These mobile units remove and destroy airborne viral particles and droplets; the latter are widely believed to be the vector for SCoV transmission. Importantly however, it was noted that such technologies must be thoroughly evaluated to determine their suitability for containing SARS in a variety of clinical settings before they are recommended for use.