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Coronavirus (COVID-19 [2019-nCoV], SARS, MERS)

Reviewed on 9/25/2020

What Facts Should You Know About Coronaviruses?

Coronaviruses include the Wuhan coronavirus (2019-nCoV), SARS, and MERS, among others.
Coronaviruses include COVID-19 (also termed novel coronavirus, 2019-nCoV, and SARS-CoV-2), SARS, and MERS, among others.
  • Coronaviruses are very common. Most coronaviruses that infect humans cause mild symptoms like a common cold and go away on their own. Very few may cause severe disease such as viral pneumonia that may lead to death.
  • Coronaviruses spread easily from person to person by inhalation of respiratory secretions or by contact of respiratory secretions with the eyes, nose, or mouth. Rarely, fecal contamination can transmit COVID-19.
  • Frequent cleansing of hands with soap and water or alcohol-based sanitizers and avoiding crowds can help prevent infection with coronavirus, influenza, and many other upper respiratory infections. Experts also recommend that people cough or sneeze into their elbow or cover their mouth and nose with a tissue that they can throw away.
  • Coronaviruses also infect animals. Some strains can also infect humans or evolve the ability to spread to humans.
  • There are seven known coronaviruses that infect people, including the recently discovered 2019 novel coronavirus (SARS-CoV-2 or 2019-nCoV), Middle East respiratory syndrome coronavirus (MERS-CoV), and severe acute respiratory syndrome coronavirus (SARS-CoV).
  • MERS-CoV, SARS-CoV, and SARS-CoV-2 (2019-nCoV) made the news in recent years because they evolved and have the ability to spread from animals to humans and because they caused deaths.
  • Researchers believe that MERS-CoV spread from camels in Saudi Arabia in 2012.
  • Researchers believe that SARS-CoV spread from bats and civet cats in China in 2002.
  • It is believed that an animal source of SARS-CoV -2 (2019 novel coronavirus, 2019-nCoV) first infected humans at a market that sells live animals for food in Wuhan, Hubei Province, China, in 2019.

What Is a Coronavirus?

Coronaviruses belong to the Coronaviridae family of viruses and are named for the crown of spikes on their surface. There are four known subgroups: alpha, beta, gamma, and delta coronaviruses. There are very many coronaviruses in nature, and they infect a variety of animals, humans, or both. Researchers have detected over 70 coronavirus species in bats alone in China. Researchers first recognized coronaviruses that infect humans in the 1960s. They generally spread in respiratory secretions between animals, animals to people, or person to person. New coronaviruses may occasionally spread from animals to cause infections in humans. This happened with MERS-CoV (from camels), SARS-CoV (bats or civet cats), and likely SARS-CoV-2 (bats).

To date, seven coronaviruses that infect people are known:

  1. 229E (alpha coronavirus)
  2. NL63 (alpha coronavirus)
  3. OC43 (beta coronavirus)
  4. HKU1 (beta coronavirus)
  5. MERS-CoV (a beta coronavirus that causes Middle East respiratory syndrome, or MERS)
  6. SARS-CoV (a beta coronavirus that causes severe acute respiratory syndrome, or SARS)
  7. SARS-Cov-2 or SARS-CoV2 or 2019 novel coronavirus (2019-nCoV) (a beta coronavirus similar to SARS-CoV)

Most human infections in the past have been due to the first four coronaviruses listed. They commonly cause "common cold" symptoms and do not cause deaths. Researchers believe the last three only recently evolved to infect humans and have caused outbreaks associated with deaths. It is possible that they may cause more severe disease because they are new coronaviruses that most human immune systems do not have prior antibodies to and are unaccustomed to. Most domestic pets such as dogs and cats are not known to spread serious coronavirus infections to humans. However, animals raised for food and sold at live animal markets have spread coronaviruses such as SARS-CoV, MERS-CoV, and probably SARS-CoV2 (2019-nCoV). Domestic cats and dogs have rarely been infected with SARS-CoV2 but are not believed to be a common source of transmission to humans.

In 2012, researchers first identified MERS-CoV in humans and traced it to markets and livestock farms in Saudi Arabia, where people raise camels for milk and meat. Outbreaks, including spread to other countries, have originated in the Arabian Peninsula. About 3-4 out of 10 infected people have died from it. In 2002, researchers first identified SARS-CoV in Guangdong Province in southern China. It caused a global outbreak that ended in July 2003. Researchers suspect an animal source, possibly bats or civet cats, from a live animal food market. Smaller incidents occurred afterward, three being from laboratory accidents. SARS-CoV2 appeared in Wuhan, Hubei Province, China, and spread rapidly. Based on early information, it appears to have originated from an animal and seafood market. Investigation is yielding new information daily and is updated at CDC, 2019 Novel Coronavirus.

What Are the Risk Factors for a Coronavirus Infection?

Risk and complications vary according to the species of coronavirus. The main risk factor for a coronavirus infection is exposure to the respiratory secretions of an animal or person infected with a strain that can infect humans. Coronaviruses are thus most easily spread when there is crowding and frequent contact of surfaces by many people or frequent contact with saliva and respiratory secretions. For example, child care centers and schools are often sources of upper respiratory virus infections such as coronaviruses. Workplaces, public transit, and shopping centers pose risks during an outbreak. Cold weather brings more groups and public crowding indoors and increases the risk of cold viruses like coronavirus, among many other respiratory viruses. Thus, they often peak during winter and spring.

Although there is still much to learn about the more serious coronaviruses, we know quite a bit about SARS-CoV2, because it caused a global pandemic in 2020. The infection or disease caused by SARS-CoV2 is called COVID-19. Risk factors for COVID-19 include the following:

  • Having close contact with someone who has been diagnosed with COVID-19
  • Visiting an area where SARS-CoV2 is circulating
  • Inhaling large respiratory droplets, or fine droplets in the case of activities that produce respiratory aerosols, from an infected person
  • Close contact is defined as being within 6 feet of someone infected with SARS-CoV2 for more than 15 minutes.
  • Risk of infection is dependent on volume of virus inhaled or in contact with eyes, nose, or the mouth. Inhalation is most likely to cause infection, but infectious droplets can also be transmitted to the eyes, nose, and mouth by contaminated fingers.
  • The most common source of infection is large respiratory droplets generated by someone breathing and talking within 6 feet. Fine respiratory droplets (aerosols) may travel longer distances and are caused by activities like singing in a choir, loud laughter, or some medical procedures.

MERS-CoV is not currently circulating. Risk factors for MERS-CoV generally include exposure to

  • a sick traveler returning from the Arabian Peninsula;
  • camels, camel markets, or camel meat or dairy products; and
  • travel in the Arabian Peninsula or other area, especially if involved during a known outbreak of MERS-CoV.

There are no specific risk factors for SARS-CoV at this time because it is not known to be circulating, but they have been similar to that for SARS-CoV2. Because most coronavirus infections are mild and self-limited and patients with symptoms are not expected to cause outbreaks, health care workers have been most at risk for SARS-CoV and some have died. This has happened especially early during an outbreak when infection prevention measures have not yet been established.

What Is the Incubation Period for a Coronavirus Infection?

The incubation period (the time from infection to development of symptoms) for coronaviruses varies by species. Most common cold coronaviruses cause symptoms within 2 days, but again this may vary. For example, the incubation period for SARS-CoV2 (2019-nCoV), MERS-CoV, and SARS-CoV seems to be anywhere from 2-14 days.

What Are the Signs and Symptoms of a Coronavirus Infection?

Most people have had one or more coronavirus infections and were unaware that they had a coronavirus. Most coronavirus infections, as with many respiratory viruses that circulate throughout the year, cause a self-limited cold for a few days, with typical signs and symptoms of

Often, there is no or very mild, brief fever. Symptoms resolve within a few days to a week without lasting aftereffects in mild infections.

Rarely with specific species of coronavirus (like MERS-CoV, SARS-CoV, and SARS-CoV2 [2019-nCoV]) do coronaviruses cause additional symptoms. These more severe coronaviruses may cause fever, shortness of breath, or difficulty breathing if the illness progresses to viral pneumonia or lung inflammation. With more severe infection, the viral pneumonia may cause respiratory failure (severe acute respiratory syndrome) and require mechanical ventilation support. In addition, severe infection may cause kidney failure (requiring hemodialysis), and systemic inflammatory syndrome that leads to shock and death. Depending on the coronavirus, other signs and symptoms might include

  • headaches,
  • muscle pain,
  • chills,
  • body aches,
  • nausea,
  • vomiting,
  • loss of sense of smell (anosmia),
  • repeated bouts of shaking chills,
  • loss of sense of taste (ageusia), and
  • diarrhea.

How Does a Coronavirus Spread?

Coronavirus spreads the way most cold viruses do. How it spreads is through respiratory droplet secretions containing coronavirus that come into contact with the eyes, nose, or mouth, either from breathing them in or from being rubbed into these areas by hands after touching secretions on a contaminated surface. Crowds and public places increase the opportunities for infection. Being in enclosed spaces with a lot of individuals increases exposure as well.

How Contagious Is a Coronavirus?

Most coronaviruses are as contagious as common cold viruses or influenza virus (the flu virus). In other words, they can be very contagious from person to person but not as contagious as measles. For example, direct contact of hands with secretions or breathing within 3-6 feet of a cough or sneeze is usually required. However, many researchers suggest that some SARS-CoV2 viruses are spread by aerosol and this makes the virus very contagious. People with SARS and COVID-19 should avoid public places for 10 days after onset of illness. It is not clear for how long MERS is contagious, but it is likely similar. Most close contacts of people with MERS have not become ill. COVID-19 seems more contagious than SARS or MERS.

What Are Treatments for Coronavirus Infections?

There are very limited treatments for coronavirus infections other than supportive treatment of symptoms such as fever, congestion, and discomfort. Common cold remedies such as over-the-counter medicines help improve comfort while the infection runs its course. There is no proven antiviral treatment for most coronavirus infections as yet. Severe coronavirus infections may require hospitalization and intensive care support such as mechanical ventilation and blood pressure support. Several antiviral drugs (such as remdesivir, also known as GS-5734) are under investigation. Remdesivir was studied for treating Ebola virus and has found to be somewhat effective against MERS-CoV and SARS-CoV. So far, the most helpful treatment has been anti-inflammatory treatment with corticosteroids.

Convalescent plasma is a type of therapy often used in the time before many treatments for infections were available. Convalescent plasma donated by people who have recovered from COVID-19 and have developed antibodies. These antibodies may help fight COVID-19 infection if the plasma is transfused into a person sick with SARS-CoV2. The usefulness of convalescent plasma to treat COVID-19 is still under investigation.

What Are Potential Complications of Coronavirus Infections?

Complications of coronavirus infections are very rare except in the case of immune deficiency or infection with a strain of coronavirus known to cause severe infection, like MERS-CoV, SARS-CoV, or COVID-19 (SARS-CoV2, 2019-nCoV). Complications include viral pneumonia, which may lead to severe acute respiratory failure. In addition, widespread inflammation (sepsis, or systemic inflammatory response syndrome or SIRS) may lead to shock, kidney failure, and even death in some cases. Some people may develop chronic symptoms like fatigue, weakness, shortness of breath, and other problems.

Children who recover from COVID-19 may later develop a widespread inflammatory syndrome that may mimic a rare pediatric illness called Kawasaki syndrome. Called multisystem inflammatory syndrome in children (MIS-C), it is a rare but serious condition of extreme inflammation in multiple organs, such as the brain, heart, blood vessels, lungs, kidneys, and intestines. Fever is common, in addition to rash, red eyes, abdominal pain, and swelling, and it may progress to life-threatening shock.

Is It Possible to Prevent a Coronavirus Infection? Is There a Coronavirus Vaccine?

Yes. The best way to prevent coronavirus and other respiratory viruses that often circulate at the same time is to avoid inhaling infectious respiratory secretions or touching surfaces that may be contaminated.

  • Be alert for recommendations from public health experts such as CDC, WHO, and your local health department during an outbreak of respiratory viruses.
  • Limit being in public or crowded places during winter and spring or when an outbreak of respiratory viruses is suspected.
  • Stay home if you are sick with fever or cold symptoms.
  • If you must be around other people, cover your cough or sneeze with your elbow or sleeve to avoid contaminating your hands and then contaminating objects you touch. You can also use tissues that you can throw away.
  • Wearing a cloth mask (especially two or more layers of fabric) has been shown to lower infections with SARS-CoV2 and other respiratory viruses such as flu. A mask can also keep fingers away from the nose and mouth. In some situations, public health experts may also recommend eye protection with goggles or a face shield.
  • Wash hands frequently with soap and water.
  • Use alcohol-based hand sanitizer often, especially if frequently touching potentially contaminated surfaces (for example, public keyboards, touch pads, doorknobs, elevator buttons).
  • Masks do not replace the respiratory and hand hygiene measures above.
  • Health care workers should pay close attention to public health and infection control guidance about severe respiratory virus outbreaks to reduce their risk of infection. For MERS, SARS, and COVID-19, health care workers use barriers such as gloves, gowns, masks, and eye protection.

There is no vaccine for coronaviruses at this time, but research is ongoing for a vaccine against SARS-CoV2.

Can You Get COVID-19 and the Flu at the Same Time?

Yes. Some hospitals during the COVID-19 pandemic found that up to 40% of patients had both flu and SARS-CoV2 infection. It is not unusual for people to get infected with two or more respiratory viruses during winter virus seasons. This is increasingly detected as more hospitals are able to test for multiple respiratory viruses using PCR (polymerase chain reaction) tests.

Will the Flu Vaccine Help Fight Coronavirus?

A flu shot (influenza vaccine) cannot fight coronavirus infections because flu is a different kind of virus. But it is not unusual for a person to be infected with more than one virus during respiratory virus season, and that can make a person twice as sick. Flu alone is bad enough, and a flu shot can help prevent you from getting both flu and another respiratory virus at the same time. It also may help prevent the bacterial pneumonia that often follows the flu and is responsible for many hospitalizations and deaths related to flu.

Is It Safe to Have a Coronavirus Vaccine if You Already Had a Flu Shot?

Many vaccines can be safely given together or separated by a few weeks. It depends on each vaccine and whether they might interfere with each other's effectiveness. Since several different COVID-19 vaccines are being studied, we do not yet know if they should be given at the same time as flu vaccine or if they should be given separately.

What Is the Survival Rate for Coronavirus Infections?

Almost all human coronavirus infections are self-limited and go away within a few days without specific treatment. Thus, survival rates are typically excellent except for a very few coronaviruses.

MERS-CoV: The case fatality rate is about 30%-35%.

SARS-CoV: The case fatality rate has ranged from 7%-50%, with older patients having the highest mortality.

COVID-19 (novel coronavirus, 2019-nCoV): Information is evolving as the pandemic continues. The likelihood of dying from COVID-19 depends on locality, ethnic background, economic situation, access to health care, and underlying illnesses. The older population (>55) and very old (>75) are most likely to die, but young, healthy people also have died. The volume or infectious dose of virus also seems to play a role in severity of illness and mortality. Updates are available at the CDC and WHO (see https://www.cdc.gov/nchs/nvss/vsrr/covid_weekly/index.htm).

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Reviewed on 9/25/2020
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