Coronaviruses are types of viruses that typically affect the respiratory tract of mammals, including humans. They are associated with the common cold, pneumonia, and severe acute respiratory syndrome (SARS) and can also affect the gut.
A coronavirus was first isolated in 1937 from an infectious bronchitis virus in birds that has the ability to seriously devastate poultry stocks.
These viruses are responsible for between 15 and 30 percent of common colds.
Over the last 70 years, scientists have found that coronaviruses can infect mice, rats, dogs, cats, turkeys, horses, pigs, and cattle.
This MNT Knowledge Center article will focus on the different types of human coronaviruses, their symptoms, how they are transmitted, and two particularly dangerous diseases that can be caused by coronaviruses: SARS and MERS.
Fast facts on coronaviruses
- There is no cure for the common cold.
- A coronavirus causes both SARS and MERS.
- Coronaviruses infect many different species.
- There are six known human coronaviruses.
- SARS spread from China to cause infection in 37 countries, killing 774 people.
Human coronaviruses (HCoV) were first identified in the 1960s in the noses of patients with the common cold. Two human coronaviruses are responsible for a large proportion of common colds OC43 and 229E.
Coronaviruses were given their name based on the crown-like projections on their surfaces. "Corona" in Latin means "halo" or "crown."
Among humans, infection most often occurs during the winter months as well as early spring. It is not uncommon for a person to become ill with a cold that is caused by a coronavirus and then catch it again about four months later.
This is because coronavirus antibodies do not last for a very long time. Also, the antibodies for one strain of coronavirus may be useless against other strains.
Cold- or flu-like symptoms usually set in from two to four days after coronavirus infection, and they are typically mild.
Human coronaviruses cannot be cultivated in the laboratory easily, unlike the rhinovirus, another cause of the common cold. This makes it difficult to gauge the coronavirus' impact on national economies and public health.
There is no cure, so treatments include taking care of yourself and over-the-counter (OTC) medication:
- Rest and avoid overexertion.
- Drink enough water.
- Avoid smoking and smoky areas.
- Take acetaminophen, ibuprofen or naproxen to reduce pain and fever.
- Use a clean humidifier or cool mist vaporizer.
The virus responsible can be diagnosed by taking a sample of respiratory fluids, such as mucus from the nose, or blood.
Different types of human coronaviruses vary in the severity of illness they cause and how far they can spread.
There are currently six recognized types of coronavirus that can infect humans.
Common types include:
- 229E (alpha coronavirus)
- NL63 (alpha coronavirus)
- OC43 (beta coronavirus)
- HKU1 (beta coronavirus)
Rarer, more dangerous types include MERS-CoV, which causes Middle East Respiratory Syndrome (MERS), and severe acute respiratory syndrome (SARS-CoV), the coronavirus responsible for SARS.
There has not been a great deal of research on how a human coronavirus spreads from one person to the next.
However, it is believed that the viruses transmit using secreted fluid from the respiratory system.
Coronaviruses can spread in the following ways:
- Coughing and sneezing without covering the mouth can disperse droplets into the air, spreading the virus.
- Touching or shaking hands with a person that has the virus can pass the virus from one person to another.
- Making contact with a surface or object that has the virus and then touching your nose, eyes, or mouth.
- On rare occasions, a coronavirus may spread through contact with feces.
People in the U.S. are more likely to contract the disease in the winter or fall. The disease is still active during the rest of the year. Young people are most likely to contract a coronavirus, and people can contract more than one infection over the course of a lifetime. Most people will become infected with at least one coronavirus in their life.
It is said that the mutating abilities of the coronavirus are what make it so contagious.
To prevent transmission, be sure to stay at home and rest while experiencing symptoms and avoid close contact with other people. Covering the mouth and nose with a tissue or handkerchief while coughing or sneezing can also help prevent the spread of a coronavirus. Be sure to dispose of any used tissues and maintain hygiene around the home.
Severe acute respiratory syndrome (SARS) was a contagious disease caused by the SARS-CoV coronavirus. It typically led to a life-threatening form of pneumonia.
The virus started off in the Guangdong Province in southern China in November 2002, eventually reaching Hong Kong. From there, it rapidly spread around the world, infecting people in 37 countries.
SARS-CoV is unique. It can infect both the upper and lower respiratory tract and can also cause gastroenteritis.
The symptoms of SARS develop over the course of a week and start with a fever. Early on in the condition, people develop flu-like symptoms, such as:
- dry coughing
Pneumonia, a severe lung infection, may develop afterward. At its most advanced stage, SARS causes failure of the lungs, heart, or liver.
During the epidemic, there were 8,098 confirmed cases of SARS with 774 fatalities. This is equal to a mortality rate of 9.6 percent. Complications were more likely in older adults, and half of all infected people over the age of 65 years who became ill did not survive. It was eventually brought under control in July 2003.
MERS, caused by the MERS-CoV coronavirus, was first recognized in 2012. This severe respiratory illness first surfaced in Saudi Arabia and, since then, has spread to other countries. The virus has reached the U.S., and the largest outbreak outside the Arabian Peninsula occurred in South Korea in 2015.
Symptoms include fever, breathlessness, and coughing. The illness spreads through close contact with people who have already been infected. However, all cases of MERS are linked to individuals who have recently returned from travel to the Arabian Peninsula.
MERS is fatal in 30 to 40 percent of people who contract it.