There are many different coronaviruses. Most of them cause illness in animals. However, 7 types of coronaviruses are known to cause illness in humans.
Four of these 7 human coronavirus infections involve mild upper respiratory tract illness that causes symptoms of the common cold.
However, 3 of the 7 human coronavirus infections can be much more severe and have recently caused major outbreaks of deadly pneumonia:
SARS-CoV2 is a novel coronavirus that was first identified in Wuhan, China in late 2019 as the cause of coronavirus disease 2019 (COVID-19) and spread worldwide.
MERS-CoV was identified in 2012 as the cause of Middle East respiratory syndrome (MERS).
SARS-CoV was identified in 2002 as the cause of an outbreak of severe acute respiratory syndrome (SARS).
These coronaviruses that cause severe respiratory infections are transmitted from animals to humans (zoonotic pathogens).
COVID-19 was first reported in late 2019 in Wuhan, China and has since spread extensively in China and worldwide. For current information on the number of cases and deaths, see the Centers for Disease Control and Prevention: 2019 Novel Coronavirus and the World Health Organization’s Novel Coronavirus (COVID-2019) situation reports.
Early COVID-19 infections were linked to a live animal market in Wuhan, China, suggesting that the virus was transmitted from animals being sold as exotic food to humans. COVID-19 is mainly spread from person to person through airborne droplets that are coughed or sneezed out by an infected person. People may also get a COVID-19 infection by touching something that has the virus on it and then touching their own mouth, nose, or eyes. The newly identified coronavirus that causes COVID-19 has been called SARS-CoV2 although it is slightly different from the coronavirus that causes SARS.
Doctors suspect COVID-19 in people who have flu-like symptoms and have traveled to or live in an area where they could have been exposed to the virus or who have had recent close contact with someone who may have had COVID-19.
Tests, such as a polymerase chain reaction (PCR) test, can be done on upper and lower respiratory secretions to identify the virus. In the US, these tests have recently been done only at the Centers for Disease Control and Prevention (CDC), but tests are starting to become available through certain other laboratories. People’s public health departments will be a source of local information on testing.
To help prevent transmission, people are being quarantined (isolated) when they have been exposed to people with the virus or if they test positive for the virus.
The best way to prevent infection is to avoid being exposed to this virus, which can be difficult because some infected people do not know they have the virus. The CDC recommends the following routine actions to help prevent the spread of respiratory viruses (see CDC’s Prevention and Treatment):
Washing hands often with soap and water for at least 20 seconds, especially after going to the bathroom, before eating, and after blowing the nose, coughing, or sneezing
Using an alcohol-based hand sanitizer with at least 60% alcohol if soap and water are not readily available
Always washing hands with soap and water if hands are visibly dirty
Avoiding touching eyes, nose, and mouth with unwashed hands
Avoiding close contact with people who are sick
Staying home when sick
Covering cough or sneeze with a tissue, then throwing the tissue in the trash
Cleaning and disinfecting frequently touched objects and surfaces using a regular household cleaning spray or wipe
There is no vaccine, antiviral drug, or specific treatment for COVID-19. Acetaminophen or a nonsteroidal anti-inflammatory drug (NSAID), such as ibuprofen, is given to relieve fever and muscle aches. Some people become so severely ill that they need to be treated with mechanical ventilation to assist their breathing.
The MERS virus was first detected in Jordan and Saudi Arabia in 2012. As of early 2018, there were 2,220 confirmed cases of MERS and 790 deaths. Most occurred in Saudi Arabia, where new cases continue to appear. Cases have also occurred in countries outside the Middle East, including France, Germany, Italy, Tunisia, and the United Kingdom in people who had been traveling or working in the Middle East.
An outbreak of MERS coronavirus occurred in South Korea from May to July 2015 after a South Korean man returned from the Middle East. This outbreak involved more than 180 cases and 36 deaths. Most person-to-person spread occurred in health care settings.
In May 2014, two cases were confirmed in the United States. Both were health care workers who had recently returned from the Persian Gulf. There have been no MERS cases in the United States since May 2014.
In several countries (including Egypt, Oman, Qatar, and Saudi Arabia), dromedary camels are suspected of being the primary source of infection for people, but how the virus spreads from camels to people is unknown.
The infection is more common among men and is more severe in older people and in people with an underlying chronic disorder such as diabetes or a heart or kidney disorder. The infection has been fatal in about one third of infected people.
The MERS virus is spread through close contact with people who have MERS or through airborne droplets that were coughed or sneezed out by an infected person. People are not thought to be contagious until symptoms develop. Most cases of person-to-person spread have occurred in health care workers caring for infected people.
Symptoms usually appear about 5 days (but anywhere from 2 to 14 days) after people are infected. Most people have a fever, chills, muscle aches, and cough. About one third have diarrhea, vomiting, and abdominal pain.
Doctors suspect MERS in people who have a lower respiratory tract infection and have traveled to or reside in an area where they could have been exposed to the virus or who have had recent close contact with someone who may have had MERS.
To diagnose MERS, doctors take a sample of fluids from several places in the respiratory tract at different times and test it for the virus. They also do blood tests to detect the virus or antibodies to it. Blood tests are done on all people who have had close contact with someone who may have MERS.
There is no specific treatment for MERS. Acetaminophen or a nonsteroidal anti-inflammatory drug (NSAID) such as ibuprofen are given to relieve fever and muscle aches.
Precautions are taken to prevent the spread of the virus. For example, the person is isolated in a room with a ventilation system that limits the spread of microorganisms in the air. People who go into the room must wear a special mask, eye protection, and a gown, cap, and gloves. Doors to the room should be kept closed except when people enter or leave the room, and people should enter and leave as few times as possible.
People traveling to the Middle East should check the World Health Organization (WHO) web site for travel advice (see WHO World-travel advice on MERS-CoV for pilgrimages).
Severe Acute Respiratory Syndrome (SARS)
No cases had been reported worldwide since 2004.
Symptoms of SARS resemble those of other more common respiratory viral infections (such as fever, headache, chills, and muscle aches) but are more severe.
Doctors suspect SARS only if people may have been exposed to an infected person.
If doctors think a person may have SARS, the person is isolated in a room with a ventilation system that limits the spread of microorganisms in the air.
(See also Overview of Viral Infections.)
Severe acute respiratory syndrome (SARS) was first detected in China in late 2002. A worldwide outbreak occurred, resulting in more than 8,000 cases worldwide, including Canada and the United States, and more than 800 deaths by mid 2003. No cases had been reported worldwide since 2004, and SARS (the disease, but not the virus) is considered to have been eradicated.
The immediate source was presumed to be civets, cat-like mammals, that were being sold in live animal markets as exotic food. How civets became infected is unclear, though bats are thought to be the reservoir host of the SARS virus in nature.
SARS is caused by a coronavirus. SARS is much more severe than most other coronavirus infections, which usually cause only coldlike symptoms. However, the Middle East respiratory syndrome (MERS) is another severe illness caused by a coronavirus.
SARS is spread from person to person through close contact with an infected person or through airborne droplets that were coughed or sneezed out by an infected person.
Symptoms of SARS resemble those of other more common respiratory viral infections but are more severe. They include fever, headache, chills, and muscle aches, followed by a dry cough and sometimes difficulty breathing.
Most people recovered within 1 to 2 weeks. However, some developed severe difficulty breathing, and about 10% died.
A doctor’s evaluation
Tests to identify the virus
SARS is suspected only if people who may have been exposed to an infected person have a fever plus a cough or difficulty breathing.
Tests can be done to identify the virus.
If needed, oxygen
Sometimes a ventilator to help with breathing
If doctors think a person may have SARS, the person is isolated in a room with a ventilation system that limits the spread of microorganisms in the air. In the first and only outbreak of SARS, such isolation kept the virus from being transmitted and eventually eliminated it.
People with mild symptoms need no specific treatment. Those with moderate difficulty breathing may need to be given oxygen. Those with severe difficulty breathing may need mechanical ventilation to aid breathing.