Description

• World Health Organization (WHO) clinical criteria (2003):
  • Suspect severe acute respiratory syndrome (SARS) case:
    • A person presenting after November 1, 2002, with high fever (>38°C), and
    • Cough or difficulty breathing, and
    • Close contact with SARS patient or travel criteria to SARS area (see “History”)
  • Probable SARS case:
    • A suspect case with radiographic pneumonia or respiratory distress syndrome
    • A suspect case with confirmatory laboratory studies (see “Lab“)
    • A suspect case with autopsy findings
• Centers for Disease Control and Prevention (CDC) clinical criteria (2003):
  • Early illness
    • Two or more constitutional symptoms—fever, chills, rigors, myalgia, headache, diarrhea, sore throat, or rhinorrhea
  • Mild to moderate illness
    • Temperature >100.4°F (>38°C)
    • One or more lower respiratory findings—cough, shortness of breath, or difficulty breathing
  • Severe illness
    • Clinical criteria of mild to moderate illness, and
    • One or more of the following—radiographic evidence, acute respiratory distress syndrome, or autopsy findings
• Clinical criteria for SARS must be interpreted in the context of the prevailing epidemiologic laboratory criteria as published by the WHO and the CDC.

Epidemiology

• SARS time line
  • November 2002: A series of severe idiopathic respiratory illnesses begin occurring in Southeast Asian countries (China, Hong Kong, Vietnam, and Singapore).
  • February 2003
    • The Chinese Ministry of Health notifies the WHO that 305 cases of acute respiratory syndrome of unknown etiology have occurred in Guangdong province in southern China.
    • SARS outbreak in Toronto
  • March 2003
    • CDC activates emergency operations center with first confirmed death of SARS patient.
    • CDC implicates a coronavirus (CoV) as the causative SARS agent.
  • May 2003: Deaths dramatically rise—7,761 cases, 623 deaths, 31 countries
  • June 2003: Reported cases slow—over 8,000 cases, >770 deaths, 32 countries
  • July 2003: WHO declares that the SARS epidemic is over.
  • Since July 2003, no further epidemics, but brief reemergence from accidental laboratory exposures in Singapore, Taiwan, and Beijing and from recurrent animal-to-human transmissions in Guangzhou in late 2003 and early 2004
• First emergence of an important human pathogen in the 21st century
• A decade after the emergence of SARS, Middle East respiratory syndrome (MERS) emerged.
• The ease with which SARS coronavirus (SARS-CoV) and MERS-CoV, as well as other respiratory CoVs crossed species to infect humans make it all the more likely that serious CoV outbreaks will continue to emerge.
• Final statistics of SARS epidemics:
  • Worldwide: >8,000 cases, nearly 800 deaths, >30 countries affected
  • United States: 134 suspected cases, 19 probable cases, 8 confirmed cases, no deaths, 17 states affected

Risk Factors

Transmission

• Direct or indirect contact of mucous membranes with infectious respiratory droplets or fomites; thus, simple masks and good hand hygiene are important.
• Period of infectivity: most likely during period with active symptoms (fever, cough)
• Incubation period 2 to 14 days but may be as long as 21 days; mean 6 days
• All cases can be traced to contact with individuals from Asian countries or community, spread from an individual whose illness could be traced to Asia.
• There have been no suspected SARS cases among casual contacts of the U.S. cases.
• Many health care workers were infected after providing care to SARS patients.
• No evidence that SARS is transmitted from asymptomatic individuals
• However, health care workers who developed SARS may have been a source of transmission within health care facilities during early phases of illness, when symptoms were mild and not recognized as SARS.
• There is no evidence that SARS can be spread after recovery from the disease.
• Pediatric population
  • Children pose a lower risk of transmission than do adults; only one reported case of transmission of SARS from pediatric patient
  • Vertical transmission of SARS-CoV from infected mothers to their newborns has not been observed.
  • None of the newborns had clinical, laboratory, or radiologic evidence suggestive of SARS-CoV infection.

General Prevention

• As there is no specific treatment, public health and infection control measures including contact tracing and quarantine of close contacts are paramount.
• Hospital infection control precautions:
  • Hospitalized patients meeting SARS case definition should be placed in a negative-pressure, single examination room.
  • Protective equipment appropriate for standard, contact, and airborne precautions (e.g., hand hygiene, gown, gloves, and N95 respirator) in addition to eye protection are recommended for health care workers to prevent transmission of SARS in health care settings.
• Pediatric patients with potential SARS exposure:
  • Children who have been exposed to an ill individual who is suspected of having SARS, or children who have traveled to an area where SARS is occurring, should be evaluated based on the following:
    • If well, parents should self-monitor the child’s condition for fever or respiratory tract illness. Attendance at child care or school is not restricted.
    • If the child is not well, parents should contact their physician and the child should be isolated at home.
    • If the child is not well and is experiencing breathing difficulty, he or she should be hospitalized. Health care workers should be informed before the admission so SARS precautions can be initiated.
  • Children who have been exposed to individuals who are not ill but have traveled to areas where SARS is occurring do not require isolation.
• Vaccine
  • No effective human vaccine has been developed.
  • Safety concerns exist for vaccine production workers.

Pathophysiology

The virus attaches to human receptor cells and initiates a nonspecific acute lung injury response leading to diffuse, severe alveolar damage.

Etiology

• SARS-CoV, a previously unrecognized single-stranded RNA CoV
• CoVs are a common cause of mild to moderate upper respiratory infections in humans and have occasionally been linked to pneumonia.
• Many believe that the virus originated in an animal species in China and then mutated in such a way that it was able to attach itself to human receptor cells.