What is Middle East respiratory syndrome (MERS)?
Middle East respiratory syndrome (MERS) is a viral respiratory illness caused by a coronavirus (Middle East respiratory syndrome coronavirus, or MERS-CoV) that was first identified in Saudi Arabia in 2012. Coronaviruses are a large family of viruses that can cause diseases in humans, ranging from the common cold to Severe Acute Respiratory Syndrome (SARS).
Causes
MERS-CoV is thought to be a zoonotic virus, which means it can pass from animals to humans.
Exposure to camels or camel products appears to be the main source of human infection. Antibodies to the virus have been identified in camels in Qatar, Egypt, and Saudi Arabia, and in a bat in Saudi. The presence of antibodies indicates that they have been exposed to the virus.
Human-to-human transmission has also been observed, primarily in health care settings rather than in the community.
Goats, cows, sheep, water buffalo, swine, and wild birds have been tested for antibodies to MERS-CoV, but none have yet been detected. The findings suggest that bats may transfer the virus to camels, and camels transmit it to humans.
Close contact between a person and an infected camel appears to be necessary for the transmission of MERS-CoV. It has been suggested that the virus could infect humans through the air, and through consumption of raw camel milk or uncooked camel meat.
It seems most likely that the virus transmits through the respiratory route, by air, but research suggests that it can survive in raw camel milk marginally longer than in milk of other species. This has prompted calls for further research into the possibility of it being transmitted through food.
Symptoms
A typical case of MERS includes fever, cough, and/or shortness of breath. Pneumonia is common however some people infected with the MERS virus have been reported to be asymptomatic. Gastrointestinal symptoms, including diarrhoea, have also been reported. Severe cases of MERS can include respiratory failure that requires mechanical ventilation and support in an intensive-care unit.
Some patients have had organ failure, especially of the kidneys, or septic shock. The virus appears to cause more severe disease in people with weakened immune systems, older people, and people with chronic diseases as renal disease, diabetes, cancer, and chronic lung disease. The mortality rate for people with the MERS virus is approximately 35 percent – this may be an overestimate however, as mild cases may be missed by existing surveillance systems.
Infection with MERS-CoV can also be asymptomatic. Infected people with no symptoms have been identified because they were tested for MERS-CoV during investigations among contacts of people known to be infected with MERS-CoV.
Risk factors
The following groups of people are more susceptible to MERS-CoV infection and complications:
-people with chronic diseases, such as diabetes, chronic lung disease, and heart conditions
-older people and the very young
-organ transplant recipients who are using immunosuppressive medications to stop their body from rejecting the organ
-those who are taking immunosuppressants, for example, to treat an autoimmune disease
-people whose immune system is weak, such as cancer patients undergoing treatment
Most of those who have died from the virus had other chronic medical conditions.
Treatment
There is no specific treatment or vaccine for the infection, and there is no cure, but supportive medical care can relieve symptoms and reduce the risk of complications.
Prevention
As a general precaution, anyone visiting farms, markets, barns, or other places where animals are present should practice general hygiene measures. These include regular hand-washing before and after touching animals, and avoiding contact with sick animals.
The consumption of raw or undercooked animal products, including milk and meat, carries a high risk of infection from a variety of organisms. Animal products processed appropriately through cooking or pasteurization are safe for consumption, but should also be handled with care to avoid cross-contamination with uncooked foods. Camel meat and camel milk are nutritious products that can be consumed after pasteurization, cooking, or other heat treatments.
Until more is understood about MERS-CoV, people with diabetes, renal failure, chronic lung disease, and immunocompromised persons are considered to be at high risk of severe disease from MERS-CoV infection. Especially in the Middle East, this group of people should avoid contact with dromedary camels, consuming raw camel milk or camel urine, as well as eating meat that has not been properly cooked.
Camel farm and slaughterhouse workers should practice good personal hygiene, including frequent hand washing, facial protection, and protective clothing (which should be removed after work and washed daily). Workers should also avoid exposing family members to soiled work clothing, shoes, or other items that may have come into contact with camels or camel excretions. Sick animals should never be slaughtered for consumption. People should avoid direct contact with any animal that has been confirmed positive for MERS-CoV infection.
Advice for those who travel to the Middle East
WHO does not recommend the application of any travel or trade restrictions or entry screening related to MERS-CoV. However, recommended actions are:
-advise travellers with pre-existing medical conditions to avoid contact with dromedary camels in the Middle East, and in other countries where infected dromedaries have been identified
-until more is understood about MERS-CoV, people with diabetes, renal failure, chronic lung disease, and immunocompromised persons are considered to be at high risk of severe disease from MERS-CoV infection. Therefore, these people should avoid close contact with animals, particularly dromedaries, when visiting farms, markets, or barn areas where the virus is known to be potentially circulating. General hygiene measures, such as regular hand washing before and after touching animals and avoiding contact with sick animals, should be adhered to
-advise travellers who develop a significant acute respiratory illness with fever and cough (severe enough to interfere with usual daily activities) to: minimise their contact with others to keep from infecting them; cover their mouth and nose with a tissue when coughing or sneezing, then discard the tissue in the trash after use and wash hands afterwards, or, if this is not possible, to cough or sneeze into the upper sleeves of their clothing, but not into their hands; and report to medical staff as soon as possible
-advise returning travellers from the Middle East that if they develop a significant acute respiratory illness with fever and cough (severe enough to interfere with usual daily activities) during the two weeks after their return, they should seek medical attention, immediately notify their local health authority and disclose their recent travel history
-advise persons who have had close contact with a traveller with a significant acute respiratory illness with fever and cough (severe enough to interfere with usual daily activities) and who themselves develop such an illness to report to local health authorities to be monitored for MERS-CoV infection
Adapted from WHO (Jan 18, 2018)
