Coronaviruses cause respiratory illnesses ranging in severity from the common cold to fatal pneumonia.
There are many different coronaviruses. Most of them cause infection in animals.
Seven coronaviruses cause infections in humans. Four of these cause mild upper respiratory tract illnesses that cause symptoms of the common cold.
However, 3 of these coronaviruses can cause severe, and sometimes fatal, illnesses and have caused major outbreaks of deadly pneumonia in the 21st century:
SARS-CoV-2 was first identified in late 2019 as the cause of coronavirus disease 2019 (see COVID-19).
MERS-CoV was identified in 2012 as the cause of Middle East respiratory syndrome (MERS).
SARS-CoV-1 was identified in 2003 as the cause of an outbreak of severe acute respiratory syndrome (SARS) that began in China near the end of 2002.
These 3 coronaviruses are transmitted from animals to humans. Infections that can be transmitted between people and animals are called zoonotic diseases, or zoonoses (see Introduction to Diseases Spread Between Animals and People (Zoonoses)).
Middle East Respiratory Syndrome (MERS)
MERS is caused by the coronavirus MERS-CoV. This infection causes severe flu-like symptoms.
MERS-CoV was first detected in Saudi Arabia in 2012. Since 2012, worldwide, there have been over 2,600 confirmed cases of MERS, with over 900 related deaths. Most occurred in Saudi Arabia, where new cases continue to appear. The largest known outbreak of MERS outside the Arabian Peninsula occurred in the Republic of Korea in 2015. The 2015 outbreak was linked to a traveler returning from the Arabian Peninsula. Cases have also occurred in countries throughout Europe, Asia, North Africa, the Middle East, and the United States in people who were either transferred for care or became ill after returning from the Middle East. Few cases have been reported since 2019.
Most infected people are about 52 years old, and the infection is more common among men. MERS is more severe in older adults and in people who have a disorder such as diabetes or a chronic heart or kidney disorder. The infection is fatal in about one-third of infected people.
Transmission of MERS
The MERS-CoV virus is spread through close contact with people who have MERS or through airborne droplets that are coughed or sneezed out by an infected person. People are not thought to be contagious until symptoms develop. Many cases of person-to-person spread have occurred in health care workers caring for infected people.
MERS can also be transmitted from animals to people. In several countries in the Middle East, dromedary camels carry the MERS-CoV virus but do not have symptoms. Camels can spread the virus to people through direct contact with the animals and possibly through contact with camel saliva or milk.
Symptoms of MERS
Symptoms usually appear about 5 days (but anywhere from 2 to 14 days) after people are infected. Some people do not have any symptoms.
Common symptoms include fever, chills, muscle aches, and cough. Diarrhea, vomiting, and abdominal pain are other symptoms that may occur.
Some people develop very severe symptoms and need to be hospitalized.
Diagnosis of MERS
Testing of secretions from the respiratory tract
Blood tests
Doctors suspect MERS in people who have a fever and other symptoms of 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 samples of secretions from several places in the respiratory tract, such as the nose and throat or sometimes from the lining of the airways leading to the lungs, 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 with a fever who have had close contact with someone who may have MERS regardless of whether they have other symptoms.
Treatment of MERS
Medications to relieve fever and muscle aches
Isolation
There is no specific treatment for MERS. Acetaminophen or a nonsteroidal anti-inflammatory drug (NSAID) such as ibuprofen is given to relieve fever and muscle aches.
Doctors may give antiviral medications to people who have severe symptoms and may need to be hospitalized.
Health care professionals take precautions to prevent spread of the virus among people who are hospitalized. 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 are kept closed except when people enter or leave the room, and people should enter and leave as few times as possible.
Severe Acute Respiratory Syndrome (SARS)
SARS is caused by the coronavirus SARS-CoV-1. This infection causes severe flu-like symptoms.
(See also Overview of Viral Infections.)
SARS is much more severe than most other coronavirus infections, which usually cause only cold-like symptoms. However, Middle East respiratory syndrome (MERS) and COVID-19 are other severe illnesses caused by a coronavirus.
The SARS-CoV-1 virus was first detected in China in late 2002. A worldwide outbreak occurred, resulting in more than 8,000 cases worldwide and 774 deaths by mid 2003.
SARS is spread from person to person through close contact with an infected person or through airborne droplets that are coughed or sneezed out by an infected person.
The 2002 SARS pandemic was traced to wild civets that were being sold in live-animal markets as food.
DS light photography/stock.adobe.com
The SARS-CoV-1 virus can also be transmitted from animals to people. The 2002 pandemic was traced to wild civets that were being sold in live-animal markets as food. People became infected after handling the infected civets. The civets were likely infected via contact with infected bats. Bats are natural hosts of coronaviruses.
Although no new cases have been reported since 2004, SARS is not considered eliminated because the SARS-CoV-1 virus naturally occurs in bats and could again spread from them to other animals to people.
Symptoms of SARS
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 who were infected during the 2002 pandemic recovered within 1 to 2 weeks. However, some developed severe difficulty breathing, and about 10% died.
Diagnosis of SARS
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.
Treatment of SARS
If needed, oxygen
Sometimes a ventilator to help with breathing
Isolation
People with mild symptoms do not need specific treatment. Those with moderate difficulty breathing may need to be given oxygen. Those with severe difficulty breathing may need mechanical ventilation to help them breathe.
During the first and only outbreak of SARS, health care professionals took precautions to prevent spread of the virus among people who were hospitalized. They isolated an infected person in a room with a ventilation system that limited the spread of microorganisms in the air. Anyone who went into the room wore a special mask, eye protection, and a gown, cap, and gloves. Doors to the room were kept closed except to enter or leave, and health care professionals entered or left the room as few times as possible. These precautions helped rapidly control the outbreak.
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