SARS-CoV-2 is a novel virus that first appeared in Wuhan, China, in December 2019. It is a member of the Coronaviridae family, so named for their “crown-like” appearance. It is a large family of viruses that spread from animals to humans and include diseases like Middle East Respiratory Syndrome (MERS) and Severe Acute Respiratory Syndrome (SARS).
The first coronavirus was isolated in 1937. The first human coronavirus was cultured in the 1960s from nasal cavities of people with the common cold. Four major categories of coronavirus are known by the Greek letters alpha, beta, delta, and gamma. Only alpha and beta coronaviruses are known to infect humans.
Like MERS-CoV and SARS-CoV, SARS-CoV-2 is a betacoronavirus. The most recently discovered coronavirus (SARS-CoV-2) causes coronavirus disease (COVID-19).
- SARS-CoV-2 is an enveloped, positive-sense, single-stranded RNA virus of genome size ~30kb, and is the largest known RNA virus genome.
- Coronaviruses mutate and change at a high rate; they have the highest known frequency of recombination of any positive-strand RNA virus.
- The exact time that the virus can survive on surfaces is not yet known. Initial pieces of evidence show that SARS-CoV-2 can survive up to 3 hours in droplets, 72 hours in plastic or stainless steel and 20 hours in cardboard.
- SARS-CoV-2 contains mushroom-shaped surface proteins called spike proteins which bind to Angiotensin-converting enzyme 2 (ACE2), human receptor for SARS-CoV-2, expressed by cells of the heart, lungs, kidneys, and intestines of humans.
Laboratory data suggest that infected people appear to be most infectious just before they develop symptoms (namely 2 days before they develop symptoms) and early in their illness. People who develop severe disease can be infectious for longer.
This virus can spread from infected persons to susceptible persons through respiratory droplets or aerosols generated from the nose or mouth of an infected person during coughing, sneezing, or exhaling. People can also be infected when they are exposed to these droplets or aerosols via
- Touching objects or surfaces contaminated with droplets then touching their eyes, nose, or mouth.
- Breathing in droplets from a person with COVID-19 who coughs or exhales droplets.
- The virus can also spread in poorly ventilated and/or crowded indoor settings, where people tend to spend longer periods of time. This is because aerosols remain suspended in the air or travel farther than 1 metre (long-range).
Though the virus may be present in feces in some cases, so far evidence show, the risk of catching COVID-19 from the feces of an infected person is low. Asymptomatic persons also can pass the virus to others, but its frequency and intensity are still under research/investigation.
On March 11, 2020, World Health Organization (WHO) declared coronavirus outbreak as a pandemic.
The symptoms of SARS-CoV-2 have ranged from mild symptoms to severe illness and sometimes death.
Protection of self and prevention of disease transmission
You can reduce your chances of being infected or spreading COVID-19 by taking the following precautions:
- Clean your hands with an alcohol-based hand rub or wash them with soap and water, regularly and thoroughly. Washing your hands with soap and water or using alcohol-based hand rub kills viruses that may be on your hands.
- Maintain at least 1 meter (3 feet) distance between yourself and anyone who is coughing or sneezing. Many people with COVID-19 experience only mild symptoms particularly at the early stages of the disease. Such people may just have a mild cough, and might be expelling infectious droplets while coughing. It is therefore possible to catch COVID-19 from someone who has, for example, just a mild cough and does not feel ill. So maintaining social distancing and staying more than 1 meter (3 feet) away from a person who is sick or have the previous contact with sick people or have suspicious travel/contact history is important to limit disease transmission.
- Avoid touching eyes, nose and mouth because your hands might have picked viruses while touching various surfaces knowingly or unknowingly and may transfer the virus to eyes, nose or mouth, facilitating its entry into your body.
- Make sure you, and the people around you, follow good respiratory hygiene. This includes covering your mouth and nose with your bent elbow or tissue when you cough or sneeze then disposing of the used tissue immediately.
- Stay home if you feel unwell. If you have a fever, cough, and difficulty breathing, seek medical attention and call in advance. This will not only help you to get appropriate health care but also help to prevent the spread of viruses and other infections.
- Ventilation is important: Open windows when indoors to increase the amount of outdoor air.
- Avoid traveling to places and comply with local/state regulations about social distancing, lock-down measures, etc.
- Get vaccinated: When it’s your turn, get vaccinated. Follow local guidance and recommendations about vaccination.
References and further reading
- 2019 Novel Coronavirus (2019-nCoV) Update: Uncoating the Virus; American Society for MIcrobiology
- Antimicrobials and COVID-19: Strategies for Treating a Pandemic; American Society for MIcrobiology
- Coronavirus (COVID-19); Centers for Disease Control and Prevention
- Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1; New England Journal of Medicine
- Coronavirus disease (COVID-19) Pandemic; World Health Organization