SARS: a closer look at this emerging infectious agent. (Health Policy Update).

Emerging and re-emerging infectious diseases are becoming a significant concern among public health officials.

The last 30 years saw a variety of new infectious diseases. These diseases include:

* HIV/ATDS

* West Nile virus 

* Nipah virus 

* Hantavirus 

In addition, several old nemeses returned such as antibiotic resistant tuberculosis and malaria. Recently, a new infectious agent from Asia has become the first new major infectious threat of the 21st century. Severe Acute Respiratory Syndrome (SARS) was found to be a new member in the family of coronaviruses.

The coronavirus was first discovered in late 1960s. Named for its distinctive crown-like appearance on electron microscopy, it is a single-strand RNA virus that is found to cause up to 30 percent of cases of the common cold in the United States.

Historically, the coronavirus has a benign course in humans. The virus in animals, however, often has a much more malignant course causing severe pneumonia, renal disease and other conditions in a range of animal species such as dogs, cats, chickens and pigs.

SARS first appeared in the Guangdong Providence of China in November 2002. Chinese health officials initially attempted to manage this outbreak alone and in secret but were soon overwhelmed.

In February of this year, the Chinese Center for Disease Control asked for assistance from the World Health Organization (WHO) with an outbreak investigation. At that time, about 305 cases with five deaths of an unknown atypical respiratory syndrome had been identified. (1)

The outbreak quickly spread outside mainland China to Hanoi, Vietnam, the Special Administrative Region of Hong Kong, Singapore, and later Toronto, Canada. Within a month, over 2,500 cases were reported worldwide and over 100 deaths.

Concerns were quickly raised about delays in the Chinese disease investigation and the candor with which they shared information or access to records. It was recognized that hospital workers, other care givers and family members of the affected individuals were at greatest risk of contacting the disease. By June 5, 2003, there were 8,400 cases of SARS worldwide and 775 deaths.

The U.S. Centers for Disease Control and Prevention (CDC) worked with WHO officials and samples from some of the early deaths and patients to identify a coronovirus species. Several other laboratories in other countries subsequently identified this organism. Eventually, the genome for this organism was decoded by a laboratory in Canada and later by the CDC.

Epidemiologic studies suggest that this organism jumped species and has recently been found in an exotic animal called the masked palm civet, which is used for food in the Guangdong Province of China.

It has also been found in the raccoon dog and Chinese ferret badger. Several of the food handlers in the providence were the first to come down with SAPS. Others were infected with the virus without apparent illness.

U.S. CDC case definition

The U.S. case definition on June 4, 2003, used to describe individuals who are considered to be suspect cases includes: (2) *

Clinical Criteria

* Asymptomatic or mild respiratory disease

* Moderate respiratory illness

* Temperature greater than 100.4[degrees] F

* One or more clinical findings of respiratory illness

* Radiologic evidence of pneumonia, or ARDS 

* Autopsy findings consistent with ARDS without another cause

Epidemiologic Criteria

* Recent travel within 10 days of onset of symptoms to an area with community transmission of SARS

* Close contact within 10 days of symptoms to a person with suspected or known SARS

Laboratory Criteria

* Confirmed

* Presence of antibody to SARS-CoV in specimens obtained during the acute illness or 21 days after illness onset

* Detection of SARS-CoV RNA by RT-PCR confirmed by a second PCR assay, by using a second aliquot of the specimen and a different set of PCR primers

* Isolation of SARS-CoV

* Negative

* Absence of antibody to SARS-CoV in convalescent serum obtained > 21 days after symptom onset

* Undetermined

* Laboratory testing either not performed or incomplete

Exclusion Criteria

A case may be excluded as a suspect or probable SARS case if:

* An alternative diagnosis can fully explain the illness

* The case was reported on the basis of contact with an index case that was subsequently excluded as a case of SARS provided other possible epidemiologic criteria are not present

Clinical course

The disease has an initial clinical presentation that is indistinguishable from the common cold or influenza. Diarrhea may also occur in 10 percent to 50 percent of patients. It may initially present as an intestinal disease. Because of this, health authorities rely on a travel or exposure history to help make an initial diagnosis of a suspect case.

The disease onset is generally within 10 days of exposure and in most cased runs its clinical course over two weeks. Twelve to 38 percent of patients progress to a more virulent clinical course with severe pneumonia and respiratory failure.

The mortality rate ranges from 13 percent in those under age sixty and 50 percent in those over age sixty. Children appear to show some resistance to the disease.

Diagnostic tests may demonstrate chest X-ray evidence of pneumonia. Other nonspecific findings of elevated liver function tests and leukopenia/lymphopenia have been reported.

Laboratory testing includes identifying the virus on electromicrospy, viral culture, and the presence of viral RNA by PCR in respiratory secretions, urine, stool or affected tissue; or measuring antibodies to the viral antigens by immunoflourscent antibody (IFA) or ELISA.

Response to Riboviron and high dose steroids has been mixed and no clear clinical recommendations other than supportive care have been made. (3)

Disease control

Health authorities have several options to contain the spread of contagious diseases.

* First, they advise people to postpone nonessential travel to affected regions of countries to avoid exposure.

* They also put procedures in place to educate and screen passengers leaving for or arriving from affected parts of the world where the disease is spreading. Several guidelines were developed to screen passengers before they enter commercial transports such as trains, planes and cruise vessels from affected countries.

* In addition, patient information sheets are made available to arriving passengers to inform them that they were in an affected area and provide information about the symptoms of SARS and what steps they should follow should they become ill.

* Isolation of ill patients and quarantine of incoming individuals are being used with moderate success. Canadian officials took very aggressive action to limit the spread after several people, including health care workers, became ill after caring for SARS patients or working in SARS hospitals. These measures included limiting access to the hospital, requiring temperature screens before workers were permitted to work and using strict infection control procedures in the care of patients. These procedures included negative flow rooms, controlled access, N-95 face masks, gloves and gowns.

U.S. officials asked state and local public health workers to "dust off" their quarantine plans and work with local hospitals to ensure effective plans to contain the SARS virus. President George Bush, on the advice of federal health officials, signed an executive order adding SARS to the list of diseases that health authorities use to quarantine incoming individuals to the United States and authorized custom and immigration officials to back up health authorities if necessary to forcefully detain individuals if required.

Case tracking mechanisms were used to identify case contacts. In many cases, groups were quarantined to ensure the disease was contained.

Because SARS is most commonly spread by large droplet exposure, people are encouraged to cover their nose and mouth when they cough or sneeze. Infected people are recommended to wear a surgical mask to reduce spread and to practice general hygiene measures such as frequent hand washing.

Caregivers and family members should wear the more protective N-95 mask. There is some evidence that the virus is present in other body fluids such as stool and urine and may stay viable on surfaces for at least 24 hours (maybe longer). The virus does appear to live within a narrow pH range and does better at cooler temperatures.

Because of the concern about aerosolized spread, respiratory care units and other health care settings must take special precautions where the risk of aerosolization is present. Infection on airlines has occurred but is very rare. Almost all of the cases reported to date were from a single plane.

Policy issues

Physician executives should begin now to prepare their health systems to address this new infectious disease. It is of particular importance because of the potential occupational hazard to their staff as well as patients. In several countries, hospitals and schools were dosed to contain the outbreak. This could have profound effects on the delivery of health services in a community.

Civil liability issues may be raised if quarantines begin in the United States. Recent reviews and new legislation by several states should help clarify this issue. The ability to close down hospitals for elective procedures in a region of the country would have significant effects on the service delivery system, but trade-offs will need to be made to contain the infection.

Local health systems need to ensure they have plans to contain highly infectious diseases like SARS and be on guard for new cases. Policies that ensure the isolation of suspect cases should be in place and practiced. In addition, occupational health procedures must be in place to ensure ill health workers are quickly identified, cared for and isolated to prevent further spread.

Health system planners also need to be sure they have business continuity plans in place for essential emergency services throughout the outbreak period.

Communication is critical, especially when it comes to physicians contacting hospitals to inform them that a potential patient with suspected SARS is being sent to their facility.

References

(1.) Heymann, David. Testimony before the U.S. House of Representatives Subcommittee on Oversight and Investigations, committee on Energy and commerce, May 5, 2003, www.who.int

(2.) CDC Health Update, Updated Interim U.S. case Definition for Severe Acute Respiratory Syndrome (SARS), June 4, 2003. * Note: The case definition is frequently updated & refined. Review the symptom onset table on the CDC Web site www.cdc.gov

(3.) Hodge, James. SARS and public health law: challenges, responses, and reform, testimony before the U.S. House of Representatives Subcommittee on Oversight and Investigations, committee on Energy and commerce, May 5, 2003.

Georges C. Benjamin, MD, FACP, is executive director of the American Public Health Association in Washington, D.C. He can be reached by phone at [phone] or by e-mail to [e-mail]