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What is SARS-Coronavirus-2 and COVID-19 (SARS-CoV-2)?

Updated May 28, 2024


Coronaviruses come from a large family of viruses that are known to cause infections like the common cold. Named for their crown-like spiked surfaces, these viruses are further classified into four additional sub-groups known as alpha, beta, delta, and gamma.

First identified in the mid-1960’s, there are seven known coronaviruses that can cause illness in humans. The four common coronaviruses circulating among humans are: 

  • 229E (alpha coronavirus)
  • NL63 (alpha coronavirus)
  • OC43 (beta coronavirus)
  • HKU1 (beta coronavirus)

Symptoms of common coronaviruses include cough, headache, sore throat, runny nose, fever, and general malaise. In persons with heart and lung disease, infants, older adults, and person with immune disorders, additional illnesses may include lower respiratory infections such as bronchitis and pneumonia. 

There are three human coronaviruses known to cause severe illness in humans.

The first coronavirus recognized as causing severe illness in humans was identified in 2003 and became known as Severe Acute Respiratory Syndrome (SARS). Health officials believe that the virus originated from an animal source, possibly a bat, and infected other animals prior to human transmission. The origin of this virus was traced to the Guangdong province of Southern China. Initial symptoms of SARS included headache, malaise, fever, muscle aches, shivering and diarrhea. Shortness of breath, cough, and diarrhea commonly occurred in the first or second week of illness and in serious cases, progressed rapidly to respiratory distress requiring intensive care.  The outbreak was considered contained by July of 2003, and no cases of the illness have been reported since 2004. SARS was believed to have infected 8,096 individuals and resulted in 774 deaths. 

The second, Middle Eastern Respiratory Syndrome (MERS), was identified by health officials in Saudi Arabia in September 2012. The exact origin of the virus remains unknown; however, it is believed to have originated in bats and spread to camels prior to human transmission. Classic symptoms of MERS include cough, fever, and shortness of breath. Respiratory distress requiring intensive care and mechanical ventilation occurs in severe cases. While the fatality rate of MERS is estimated at 35 percent, health officials believe that the true fatality rate is lower since milder cases are likely not diagnosed. The virus is not easily transmitted, and most infections have occurred in health care settings among personnel providing care to infected individuals. While MERS has been reported in 27 countries, 80 percent of cases have been reported in Saudi Arabia.  Only two cases of MERS have been reported in the U.S. and both involved health care providers residing and working in Saudi Arabia. 

The third and most recent is the novel SARS-Coronavirus-2 (SARS-CoV-2), which causes a collection of symptoms including severe illness that has become known as COVID-19. Initial reports began on January 8, 2020, when the CDC issued a health advisory alert regarding a cluster of pneumonia cases with links to a wholesale animal and fish market in Wuhan City, in the Hubei province of China. The initial health alert reported illness in 59 individuals with symptom onset dates beginning December 12, 2019 that included shortness of breath and fever. No deaths were reported and according to Chinese health officials, there were no reports of human-to-human transmission. 

Chinese health officials identified the virus as a novel coronavirus on December 31, 2019, and by the end of January 2020, 217 deaths among 9,776 confirmed cases had been reported. On January 30, 2020, the World Health Organization (WHO) declared the outbreak a “Public Health Emergency of International Concern” with health officials reporting that the origin of the virus was likely an unsanitary food market in Wuhan City, China. WHO officials suggested that infected individuals were exposed after consuming infected bats and snakes from the city’s market. 

The origins of SARS-CoV-2, however, has been disputed by many researchers who believe that the virus was most likely leaked from the Wuhan Institute of Virology where scientists were conducting studies on bat coronaviruses.     

COVID-19 Symptoms and Complications

Symptoms of COVID-19, the illness caused by SARS-CoV-2, include: 

  • Cough
  • Congestion
  • Runny nose
  • Shortness of breath
  • Difficulty breathing
  • Fever
  • Chills
  • Fatigue
  • Muscle aches
  • Body aches
  • Sore throat
  • Headache
  • New loss of taste or smell
  • Diarrhea
  • Nausea
  • Vomiting

Complications of the virus include pneumonia, acute respiratory failure, Acute, Respiratory Distress Syndrome (ARDS), acute kidney, liver, and heart injury, septic shock, disseminated intravascular coagulation (DIC), rhabdomyolysis (muscle breakdown), chronic fatigue syndrome, and blood clots. 

Many complications may be caused by a condition known as a cytokine storm. This occurs when an infection triggers the immune system to flood the bloodstream with inflammatory proteins referred to as cytokines, which can damage organs and kill tissue.  Health officials also believe that the virus may trigger a multisystem inflammatory syndrome in children and adolescents known as Multisystem Inflammatory Syndrome in Children (MIS-C). The CDC reports that they do not know what causes this condition but that many children who develop it have a personal health history of exposure to the SARS-CoV-2 virus or have been in contact with an infected individual.  Early in the pandemic, the CDC reported the incident rate of MIS-C to be one in 3,000 to 4,000 children and adolescents infected with SARS-CoV-2. This rate has decreased steadily throughout the pandemic and as of March 2023, MIS-C is considered rare. 

SARS-CoV-2 Variants

Multiple variants of the SARS-CoV-2 virus continue to emerge. Like all viruses, SARS-CoV-2 continually evolve due to genetic mutations during the genome’s replication, which results in a variant. 

The Centers for Disease Control and Prevention (CDC) classify SARS-CoV-2 variants into four distinct categories: Variant Being Monitored; Variant of Interest; Variant of Concern; and Variant of High Consequence. The variant’s transmissibility, the severity of illness, and the effectiveness of current medical treatments factor into the classification of each variant.

As of August 27, 2023, the Omicron variant is the predominant SARS-CoV-2 variant in the U.S. and remains a Variant of Concern.   

Public health experts admit that they are uncertain as to how effective the current authorized treatments and vaccines will be against novel SARS-CoV-2 variants.   

IMPORTANT NOTE: NVIC encourages you to become fully informed about covid-19 and the covid-19 vaccine by reading all sections in the Table of Contents, which contain many links and resources such as the manufacturer product information inserts, and to speak with one or more trusted health care professionals before making a vaccination decision for yourself or your child. This information is for educational purposes only and is not intended as medical advice.

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