Charles John Palenik, MS, PhD, MBA
Recently, an excellent review of how the severe acute respiratory syndrome (SARS) epidemic could be used to prepare for future disease outbreaks (Weinstein, RA. "Planning for Epidemics — The Lessons Learned From SARS." N Eng J Med 350:2332-2234, 2004) was published. The article reviewed how SARS spreads and how the world health community responded. During the process, a significant number of epidemiological lessons were learned, both positive and negative.
The SARS epidemic covers events from November 2002 through July 2003. A total of 8,098 persons worldwide became ill with SARS, accompanied by either pneumonia or respiratory-distress syndrome. By late July 2003, no new cases were being reported. SARS is caused by a previously unrecognized virus called SARS-associated coronavirus (SARS-CoV). Other infectious agents may possibly have had a supportive role in some cases of SARS.
The original spread of SARS was from an obscure animal to food-handlers in a rural area of Southern China. The disease moved to Hong Kong through an infected physician who was attending a wedding. Although the physician spent only one night in a hotel, SARS was spread to 12 other people. These people eventually returned to five different countries. Eventually, there would be 774 deaths in 27 countries on six continents.
The lessons learned from the SARS epidemic should help in preparing for future epidemics. These lessons include:
• Animal pathogens (e.g., SARS coronavirus, West Nile virus, monkey pox, avian influenza virus, or prions of bovine spongiform encephalopathy (mad cow disease) can cause serious zoonoses or animal to human spread.)
• Modern forms of transportation mean that a disease present today in remote areas of the world can spread anywhere within 24 hours.
• The ability of molecular virology is incredible. Within weeks, the etiological agent of SARS was identified and its genetic code determined.
• Transmission routes can be determined through the use of epidemiological histories.
• International, national, and local health agencies can and do cooperate to meet the demands of an emerging disease.
• Basic infection control works. Protect the patient and protect the practitioner; however, SARS is not forgiving when lapses in clinical or laboratory infection control occur
• History can be changed by a single person. The SARS epidemic was spread by an ill physician who survived, while the physician who alerted the world health community succumbed to the disease.
The spread of SARS was more easily contained because of the nature in which the virus is commonly spread. Disease transmitted by airborne routes, such as measles or chicken pox, can be readily spread and pose a significant epidemic risk to persons without immunity. SARS appears to be best spread through respiratory droplets. Aerosols are very light and can remain suspended for extended periods of time. Droplets are heavier and fall quickly. Thus, SARS requires close contact for transmission. Infection is thought to occur within three feet of an infected person. SARS-associated coronavirus can survive on inert environmental surfaces. The virus also can be recovered from the human stool. This suggests the possibility of transmission from contact with infected fomites.
Fortunately, SARS does not seem to be communicable prior to the onset of symptoms. Also, the infectivity of a person seems to rise as he or she becomes more ill. Most cases of SARS occurred in households of persons with imported infections, and in hospitals.
It seems inevitable that new diseases will continue to appear and that other known infections will reappear (recrudescence) at intervals of their choice. Quick response and insightful reaction are extremely valuable. However, proactive preventive measures, planning, and practicing are of even greater value.
A significant point to remember from the SARS epidemic is that even in the absence of diagnostic tests and the nonpathognomic clinical presentation initially present, the use of proper epidemiological methodology — especially the use of medical histories — are invaluable. All recent high-profile epidemics were first identified by alert clinicians.
OSAP, the Organization for Safety & Asepsis Procedures, is dentistry's prime source for evidence-based information on infection control and prevention and on human safety and health. Further information on SARS and other emerging diseases is available on the OSAP Web site — www.osap.org.
Dr. Charles John Palenik is an assistant director of Infection Control Research and Services at the Indiana University School of Dentistry. Dr. Palenik has authored numerous articles, book chapters, and monographs, and is the co-author of the popular Infection Control and Management of Hazardous Materials for the Dental Team. He serves on the Executive Board of OSAP, dentistry's resource for infection control and safety. Questions about this article or any infection-control issue may be directed to [email protected].