Last Reviewed
January 18, 2021

Severe Acute Respiratory Syndrome (SARS)

The betacoronavirus that causes severe acute respiratory syndrome (SARS) --  is a viral respiratory illness caused by a coronavirus called SARS-associated coronavirus (SARS-CoV). Currently, there is no known SARS transmission anywhere in the world.

SARS-CoV was the first major novel infectious disease to hit the international community in the 21st century. SARS challenged all affected countries' public health systems and reported a 2009 study.

SARS-COV-1 is a different coronavirus than the SARS-CoV-2, which the WHO identified in 2019.

A study published by the NEJM on April 16, 2020, found that the stability of SARS-CoV-2 was similar to that of SARS-CoV-1 under certain circumstances tested. This indicates that differences in these viruses' epidemiologic characteristics probably arise from other factors, including high viral loads in the upper respiratory tract and the potential for persons infected with SARS-CoV-2 to shed and transmit the virus while asymptomatic.

SARS-CoV Outbreak Timeline

2003 - SARS was first reported in Asia in February and became a notifiable disease in mid-April China. As of July 2003, the WHO reported 325 cases, and the illness spread to about 24 countries in North America, South America, Europe, and Asia during 2003.

2003 - SARS has not re-emerged naturally, but there have been 6 escapes from virology labs: 1 event each in Singapore and Taiwan, and 4 separate escapes of the coronavirus at the same laboratory in Beijing, China.

2004 - The WHO published during October the 'SARS Risk Assessment and Preparedness Framework.' And, the CDC issues “Notice of Embargo of Civets.” A SARS-like virus had been isolated from civets (captured in China's areas where the SARS outbreak originated). CDC banned the importation of civets, which remains in effect.

2005 - A pre-clinical study finds chloroquine effectively inhibits the infection and spread of SARS CoV in cell culture. Similar studies describe these proteins' roles in SARS-CoV replication and potential therapeutic strategies to prevent SARS-CoV entry into target cells.

2005 - Microbiologist Kwok-yung Yuen of the University of Hong Kong (HKU) and colleagues sampled monkeys, rodents, and several bat species in Hong Kong's hinterlands. The SARS-like virus was found in 39% of the anal swabs collected from Chinese horseshoe bats, both eaten and used in traditional Chinese medicine. Also, around 80% of serum samples collected from the bats showed antibodies to the virus.

SARS-CoV Overview

Human coronavirus was initially cultured in the 1960s from nasal cavities of people with the common cold, reports a recent study. They are the 2nd leading cause of the common cold after rhinoviruses. People worldwide commonly get infected with human coronaviruses 229E, NL63, OC43, and HKU1 say the CDC. The discovery of bat SARS-like coronaviruses and the great genetic diversity of coronaviruses in bats have shed new light on SARS coronaviruses' origin and transmission.

There are four main sub-groupings of coronaviruses, known as alpha, beta, gamma, and delta. SARS-CoV is a betacoronavirus, like MERS.

The incubation period for SARS is typically 2 to 7 days, although in some cases, it may be as long as 10 days. In a tiny proportion of cases, incubation periods of up to 14 days have been reported. The WHO estimates that the SARS case fatality ratio ranges from 0% to 50%, depending on the age group affected.

During the SARS outbreak in 2004 in China, SARS-CoV RNA was detected in 100% of untreated and 30% of disinfected wastewater samples collected from a hospital in Beijing, China receiving SARS patients (Wang et al., 2005). 

The U.S. CDC published a report in December 2006 that concluded 'Bats have been identified as a natural reservoir for an increasing number of emerging zoonotic viruses, including henipaviruses and variants of rabies viruses. Recently, another group and we independently identified several horseshoe bat species as the reservoir host for many viruses that have a close genetic relationship with the coronavirus associated with severe SARS. Our current research focused on identifying the reservoir species for the progenitor virus of the SARS coronaviruses responsible for outbreaks during 2002–2003 and 2003–2004. In addition to SARS-like coronaviruses, many other novel bat coronaviruses, which belong to groups 1 and 2 of the 3 existing coronavirus groups, have been detected by PCR.

SARS-CoV Treatments

A study published in 2015 suggest that convalescent plasma may have a clinically relevant impact in reducing the rate of mortality and viral load in patients with SARI of viral etiology. Post hoc pooled meta-analysis across all viral etiologies showed a statistically significant 75% reduction in the odds of mortality among those treated with convalescent plasma or serum. We found no evidence of serious adverse events or complications due to therapy and limited evidence of a reduction in the use of critical care resources and the length of hospital stay.

A study published in 2014 summarized saying 'Convalescent plasma may reduce mortality and appears safe. This therapy should be studied within the context of a well-designed clinical trial or other formal evaluation, including for treatment of Middle East respiratory syndrome coronavirus CoV infection.'

A study published by the NIH in 2006 found the absence of the coronavirus outside the lungs suggests that death is the result of SARS-CoV replicating in the lungs alone. Whether SARS-CoV fatally damages lung tissue directly or whether macrophages recruited to the lungs in response to infection with SARS-CoV cause fatal immunopathological changes remains an open question.

A study published in 2005 found 'all infected healthcare workers whose SARS condition had progressed severely and who had failed to respond to the available treatment, survived after transfusion with convalescent plasma.

SARS-CoV Sources

A 2015 study suggests a potential risk of SARS-CoV re-emergence from viruses currently circulating in bat populations. The results indicate that group 2b viruses encoding the SHC014 spike in a wild-type backbone can efficiently use multiple orthologs of the SARS receptor human angiotensin-converting enzyme II (ACE2), replicate efficiently in primary human airway cells, and achieve in vitro titers equivalent to epidemic strains of SARS-CoV.

A study published in 2007 found horseshoe bats are the natural reservoir for the SARS-CoV-like virus. Civets are the amplification host, highlighting the importance of wildlife and biosecurity in farms and wet markets, serving as the source and amplification centers for emerging infections.

SARS-CoV Gender Differential

To investigate gender differences, during 2019, researchers infected male and female mice of different age groups with SARS-CoV and analyzed their susceptibility to the infection. Our results showed that male mice were more susceptible to SARS-CoV infection than age-matched females.

The degree of sex bias to SARS-CoV infection increased with advancing age, such that middle-aged mice showed much more pronounced differences than young mice. Enhanced susceptibility of male mice to SARS-CoV was associated with elevated virus titers, enhanced vascular leakage, and alveolar edema. These changes were accompanied by increased accumulation of inflammatory monocyte macrophages and neutrophils in male mice's lungs, and depletion of inflammatory monocyte macrophages partially protected these mice from lethal SARS. Moreover, the sex-specific differences were independent of T and B cell responses.

Furthermore, ovariectomy or treating female mice with an estrogen receptor antagonist increased mortality, indicating a protective effect for estrogen receptor signaling in mice infected with SARS-CoV. Together, these data suggest that sex differences in SARS-CoV's susceptibility in mice parallel those observed in patients and identify estrogen receptor signaling is critical for females' protection.

NOTE: This page's content is sourced from the CDC, WHO,, and the Precision Vax news network. This information was last fact-checked by healthcare providers, such as Dr. Robert Carlson.