Disease & Vaccine Information

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

Updated July 20, 2022


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.  One day later, the U.S. Department of Health and Human Services (HHS) Secretary Alex M. Azar II declared the novel coronavirus a U.S. public health emergency. 

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. 

COVID-19 Broadly Defined to Include all SARS-CoV-2 Infections

According to the CDC’s August 5, 2020 interim case definition for Coronavirus Disease 2019 (COVID-19), a confirmed COVID-19 case is one where laboratory evidence indicates the presence of the SARS-CoV-2 virus by a molecular amplification test  such as reverse transcriptase quantitative polymerase chain reaction (RT-qPCR) or nucleic acid amplification test (NAAT). 

A probable COVID-19 case is a case where a person meets the clinical criteria for COVID-19 illness based on at least one symptom and the individual is also epidemiologically linked to another confirmed or probable case. The criteria for epidemiological linkage include close contact with a confirmed or probable case of COVID-19 disease or else being considered at risk based on criteria defined by public health officials during an outbreak. Probable cases are also cases confirmed by antigen testing, a rapid test considered less sensitive and not as reliable as molecular amplification tests.   

SARS-CoV-2 Variants

Multiple variants of the SARS-CoV-2 virus emerged in the fall of 2020 and continue to circulate worldwide.  On May 31, 2021, the World Health Organization (WHO) announced the use of “simple, easy-to-say labels for SARS-CoV-2 Variants of Interest and Concern” and reported that letters of the Greek alphabet would be used to identify variants. While scientific names would continue to be used, WHO reported that: 

“While they have their advantages, these scientific names can be difficult to say and recall, and are prone to misreporting. As a result, people often resort to calling variants by the places where they are detected, which is stigmatizing and discriminatory. To avoid this and to simplify public communications, WHO encourages national authorities, media outlets and others to adopt these new labels.”

In the United Kingdom, the B.1.1.7 variant (Alpha) emerged in September 2020, and by  January 2021, it was determined to be the dominant circulating strain in England. The transmissibility of this variant was reportedly greater than other circulating SARS-CoV-2 virus variants.  As of the fall of 2021, the CDC has labeled the Alpha Variant as a Variant Being Monitored and is continuing to monitor for SARS-CoV-2 cases associated with the variant.    Health officials report that this variant appears to be 30 to 80 percent more transmissible and increased a person’s risk of death by 30 percent.   

The B.1.351 variant (Beta) was initially detected in Nelson Mandela Bay in South Africa in early October, 2020. By December 2020, this variant was found to be the predominant variant circulating in Zambia. It is not currently reported to be associated with an increase in disease severity.  The CDC has labeled the Beta Variant as a Variant Being Monitored.   

The P.1. variant (Gamma) was first detected in Japan in four travelers from Brazil. In late December 2020, 42 percent of positive samples collected in Manaus, the largest city in the Amazon region of Brazil, were the P.1. variant. Public health officials have expressed concerns that this variant may be transmitted more effectively or be responsible for re-infection.   The CDC has labeled the Gamma Variant as a Variant Being Monitored.   

On February 11, 2021, the Journal of the American Medical Association (JAMA) published a letter from researchers reporting on the novel SARS-CoV-2 variant  CAL.20C (now B.1.427/B.1.429 or Epsilon), that had emerged in late 2020 in Southern California. By mid-January 2021, this variant was found to account for 35 percent of SARS-CoV-2 specimens from California, and 44 percent of specimens from Southern California. The infectiousness of this strain or its impact on disease severity was reported as unknown.   

Another variant, the B.1.526 variant (Iota), was identified by research teams from Columbia University and the California Institute of Technology (CalTech). Findings by these teams have been pre-published separately and await peer review.    Both papers indicate that the strain was detected in New York in November 2020 and that the variant may represent an antigenic drift in the virus with possible blunting of current vaccine effectiveness. The Columbia paper indicated that those impacted by this variant “were on average older and more frequently hospitalized”,  while the CalTech paper estimated that the variant accounted for approximately 25 percent of all specimens in February 2021.  The CDC has labeled the Iota variant a Variant Being Monitored and is continuing to monitor for SARS-CoV-2 cases associated with the variant.   

On May 4, 2021, the CDC classified the SARS-CoV-2 variant B.1.617 (Delta) and it’s three sub lineages, B.1.617.1, B.1.617.2, and B.1.617.3, as Variants of Interest.  These variants, which originated in India, were declared Variants of Concern by the World Health Organization (WHO) on May 10, 2021. According to the WHO, these variants are associated with increased transmissibility and decreased neutralization. As a result, vaccinated individuals and persons who have previously recovered from a COVID-19 infection may be at risk for infection from this variant.  A technical briefing published by Public Health England on June 11, 2021 noted that almost one third of individuals who died with the Delta variant were fully vaccinated.  In the June 18, 2021 Public Health England Technical report, the death rate in fully vaccinated individuals was 6.6 times higher than among unvaccinated people. 

By the end of June 2021, almost 90 percent of COVID-19 cases in Israel were reported as being from the Delta variant, with 50 percent occurring in fully vaccinated adults.  Health experts have acknowledged that vaccinated individuals are capable of spreading the virus on to others, as COVID-19 vaccines are unable to stop viral transmission. 

In July 2021, the CDC reported that a SARS-CoV-2 outbreak in Massachusetts where most cases were of the Delta variant, 74 percent of cases occurred among fully vaccinated individuals. Additionally, of the five outbreak associated hospitalizations, four occurred in fully vaccinated persons.  Another CDC study published in mid-August 2021 found that among persons residing in nursing care facilities, two doses of mRNA vaccines were only 53.1 percent effective against the Delta variant. 

As of September 28, 2021, the CDC has reported that the Delta variant was the predominant strain in the U.S., and was more than twice as contagious as previous variants.  The Delta variant has been labeled a Variant of Concern and the CDC is continuing to monitor the spread of this variant.   

The C.37 variant (Lambda), first identified in Peru in August 2020, was classified by WHO as a Variant of Interest on June 14, 2021.  A pre-print study posted on bioRxiv ahead of peer review in late July 2021 reported the Lambda variant to be highly contagious and more resistant to vaccines. 

On August 30, 2021, WHO designated the Mu variant a Variant of Interest.  Initially identified in Columbia in January 2021, this variant, also known as B.1.621, has become increasingly prevalent in South America. WHO reports that "the Mu variant has a constellation of mutations that indicate potential properties of immune escape," but state that further studies are needed on the variant. As of September 2, 2021, nearly all US states had reported the Mu variant.  As of September 28, 2021, the Mu variant has been designated as a Variant Being Monitored by the CDC. 

Health experts admit that they are uncertain as to how effective the current authorized treatments and vaccines will be against these novel 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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