Understanding MERS-CoV: Deadly Coronavirus Symptoms and Safety Measures
The Agents
SARS (severe acute respiratory syndrome) and MERS (Middle East respiratory syndrome) are serious infectious respiratory diseases caused by members of a group of viruses known as coronaviruses. The name coronavirus comes from the appearance of the virus under the microscope because it has a spiky or crown-like appearance. Both viruses can be deadly to humans.
SARS is caused by SARS-associated coronavirus (SARS-CoV), while MERS is caused by Middle East respiratory syndrome coronavirus (MERS-CoV).
SARS-CoV emerged nearly two decades ago in China and spread rapidly to other countries. Fortunately, it was successfully contained and no new cases have been reported since the initial outbreak. MERS-CoV emerged in 2012 in Saudi Arabia and spread throughout the Middle East and to other parts of the world including the United States, Europe, Africa, and Asia. The number of new infections has since decreased significantly.
Later in 2019, another coronavirus called SARS-CoV-2 emerged in Wuhan, China. It causes the disease known as COVID-19. Unlike SARS-CoV and MERS-CoV, SARS-CoV-2 spread rapidly around the world and resulted in a global pandemic.
SARS
SARS was first identified in Guangdong Province, China in November 2002. It spread quickly to other areas including Hong Kong, Vietnam, Singapore, Taiwan, and Toronto, Canada during the first half of 2003.
SARS is characterized by severe pneumonia-like symptoms that can be fatal. SARS-CoV spread mainly through respiratory droplets produced when an infected person coughed or sneezed and through contact with contaminated surfaces.
- More than 8,000 people were infected with SARS-CoV.
- More than 800 deaths were reported worldwide.
The scientific response to SARS was extremely rapid. Within weeks of the outbreak:
- The virus causing the disease was identified.
- Diagnostic tests were developed.
- The complete genome of the virus was sequenced.
Researchers found evidence that the first infected individuals had contact with wild animals in Chinese markets, especially palm civets carrying closely related coronaviruses. The virus likely adapted to humans through mutation, making human-to-human transmission more effective and triggering the SARS epidemic.
Fortunately, the SARS outbreak was short-lived. Public health control measures and coordinated responses helped prevent further spread.
Before SARS-CoV appeared, coronaviruses were generally known to cause mild respiratory illnesses in humans. SARS-CoV was unusual because it caused severe respiratory disease and death.
Scientists believe SARS-CoV may interfere with a protein system that regulates body fluid balance. This can allow fluid to leak into the lungs, leading to severe respiratory illness.
MERS
MERS-CoV emerged in 2012 in the Arabian Peninsula. Although different from SARS-CoV, the disease caused by MERS is similar because it also causes severe respiratory illness that can be fatal.
The mortality rate for MERS is approximately 35%, although this may be overestimated because mild cases may not have been reported.
The following groups are considered at higher risk for severe illness:
- People with diabetes
- Individuals with kidney failure
- People with chronic lung disease
- Immunocompromised individuals
- Elderly people
Like SARS, MERS is believed to have originated in bats. However, dromedary camels became the primary source of human infection.
MERS-CoV can spread to people who come into close contact with infected individuals, especially healthcare workers and family members. However, the virus does not spread easily from person to person.
Global Spread of MERS
Most MERS cases have occurred in Saudi Arabia, although infections have also been reported in Europe, Asia, Africa, and North America.
- Two unrelated cases were confirmed in the United States in May 2014.
- In May 2015, South Korea reported the first human-to-human transmission outside the Middle East.
- By May 2020, more than 2,500 laboratory-confirmed cases had been reported worldwide.
- Approximately 900 deaths were associated with MERS-CoV.
- Cases had been reported in 27 countries since 2012.
- About 80% of cases occurred in Saudi Arabia.
The Problem
Currently, there are no approved vaccines or specific treatments for SARS or MERS, although several vaccines and medicines are under development.
Even though there are no known human SARS cases today, another outbreak could still occur. Scientists believe SARS-CoV may still exist in animal hosts in the wild.
Researchers identified the Chinese horseshoe bat as a likely natural reservoir for SARS-CoV. Genetic studies showed strong similarities between bat coronaviruses and the human SARS virus.
MERS-CoV continued to spread at very low levels through 2020, meaning future outbreaks remain possible.
The 2015 MERS outbreak in South Korea demonstrated how quickly infectious diseases can spread internationally.
A traveler returning from the Middle East carried the virus into South Korea. The disease spread rapidly through a hospital setting before it was identified.
- More than 180 infections were reported.
- Over 30 deaths occurred.
- Schools and businesses were temporarily closed.
- People avoided public places due to fear of infection.
The outbreak highlighted the importance of:
- Rapid disease detection
- Immediate infection control measures
- Isolation of infected individuals
- Monitoring close contacts
The Research
After the 2003 SARS outbreak, researchers at Baylor College of Medicine established a SARS-CoV research program focused on:
- Understanding disease development
- Developing vaccines
- Conducting clinical trials
Scientists tested vaccine candidates against SARS-CoV in animals including ferrets, mice, and nonhuman primates. Although the vaccines provided protection against infection, some caused lung damage in mice, making them unsuitable for human use.
Protein-Based Coronavirus Vaccines
Texas Children’s Center for Vaccine Development, led by Dr. Peter Hotez and Dr. Maria Elena Bottazzi, received funding to develop recombinant protein-based vaccines for SARS and MERS.
The vaccines targeted a section of the coronavirus spike protein called the receptor-binding domain (RBD).
The goal was to stimulate neutralizing antibodies that could block the virus from attaching to human cells and prevent infection.
Researchers found that optimized RBD vaccine candidates produced stronger antibody responses and higher levels of neutralizing antibodies in vaccinated animals.
These findings later contributed to the development of vaccines against SARS-CoV-2, the virus responsible for COVID-19.
Scientists continue to support coronavirus vaccine research to help prevent future outbreaks and improve global biodefense preparedness.
For More Information
- Information about MERS-CoV from the CDC
- Information about SARS from the WHO
- Basic information about SARS from the CDC
- Information about SARS from the National Institutes of Health
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