SARS will it return ?

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SARS –CoV

Severe Acute Respiratory syndrome Corona virus

What are corona viruses?
Large, enveloped, positive sense single-stranded RNA viruses that replicate in the cytoplasm of animal host
What diseases caused by corona viruses in human?
· Human coronaviruses (HCoVs) were previously only associated Mild respiratory illnesses. (One-third of colds are caused by coronaviruses ).
l Viruses that infect epithelial cells of the enteric tract cause diarrhea. This can occur in human neonates .
l Most people harbor anti-coronavirus antibodies but reinfection is common indicating that there are many circulating serotypes of the virus in the human population
l They can occasionally cause serious infections of the lower respiratory tract in children and adults and necrotizing enterocolitis in newborns
What is the aetiology of SARS (Severe Acute Respiratory Syndrome)?
The etiologic agent of SARS was identified in late March 2003, when laboratories in Hong Kong, the United States, and Germany found evidence of a novel coronavirus in patients with SARS. This evidence included isolation on cell culture, demonstration by electron microscopy, demonstration of specific genomic sequences by polymerase chain reaction (PCR) and by microarray technology, as well as indirect immunofluorescent antibody tests.

Three weeks later, on April 16, 2003, following a meeting of the collaborating laboratories in Geneva, the WHO announced that this new coronavirus, never before seen in humans or animals, was the cause of SARS .This announcement came after research done by the then 13 participating laboratories from ten countries had demonstrated that the novel coronavirus met all four of Koch’s postulates necessary to prove the causation of disease:
1. The pathogen must be found in all cases of the disease;
2. It must be isolated from the host and grown in pure culture;
3. It must reproduce the original disease when introduced into a
susceptible host;
4. It must be found in the experimental host so infected.

What is the Natural Host of SARS CoV ?
Sequencing of viruses isolated from some animals ( masked palm civets) demonstrated that, with the exception of a small additional sequence, the viruses are identical to the human SARS virus.
Stability and Resistance of SARS –CoV
l The virus is more stable than the other known human coronaviruses
l The virus is stable in feces and urine at room temperature for at least 1-2 days. higher in stools from patients with diarrhea (the pH of which is higher than that of normal stool).


SARS Co-V has been detected in:
l High concentrations of viral RNA of up to 100 million molecules per milliliter were found in sputum .
l SARS-associated coronavirus RNA was detected in nasopharyngeal aspirates by RT-PCR in 32% at initial presentation (mean 3.2 days after onset of illness) and in 68% at day 14 .
l In stool samples, viral RNA was detected in 97% of patients two weeks after the onset of illness &42% of urine samples were positive for viral RNA .However in during the late convalescent phase, the virus was detected at extremely low concentrations in feces suggesting that may be shed in feces for prolonged periods of time .
· Viral RNA was also detected at extremely low concentrations in plasma during the acute phase.

Clinical course

· The incubation period of SARS is short. six days , ranging from 2 to 16 days
· 1. Week 1: was characterized by fever, myalgia, and other systemic symptoms that generally improved after a few days. In terms of disease progression, all except one patient became afebrile within 48h using the standard treatment protocol, consisting of intravenous amoxicillin-clavulanate, oral azithromycin, intravenous ribavirin and a tailing regimen of corticosteroids.
· 2.week 2: the patients frequently had recurrence of fever, onset of diarrhea, and oxygen desaturation.Fever recurred in 85% of the patients at a mean of 8.9 days. Radiological worsening was noted in 80% at a mean of 7.4 days: Nearly half the patients developed shifting of radiological lesions,evidenced by improvement of the original lesions followed by the appearance of new lesions. IgG seroconversion, apparently correlating with falls in viral load, could be detected from day 10 to 15. Severe clinical worsening also occurred at this time.
· 3. Third phase 20% of patients progressed to the, characterized by ARDS necessitating ventilatory support. Several patients developed nosocomial sepsis during this phase of end-organ damage and severe lymphopenia

· Atypical Presentation

· There are several reports on atypical clinical presentations of SARS.
· Patients may present without fever, or with diarrhea but no pneumonia emphasizing the difficulties in identifying SARS without a reliable diagnostic test.

Diagnostic Tests

Molecular test-Virus isolation -Antibody detection

Will it return?

It is completely unclear at present (early September 2003) whether SARS will reappear. Clinically "silent" infections and long-term carriage can not be ruled out completely and may result in further outbreaks, perhaps in a season-dependent manner. It is also likely that SARS-CoV or a closely related coronavirus persist in an unidentified animal reservoir from where it may again spill over into the human population. Therefore, it is vital that vigilance for new SARS cases be maintained