Generality
Middle East Respiratory Syndrome (MERS) is an infectious disease caused by a Coronavirus (MERS-CoV) identified for the first time in 2012, in Saudi Arabia.
MERS manifests itself with clinical features ranging from asymptomatic or mild illness to acute respiratory distress syndrome, up to multi-organ failure leading to death; the chances of a fatal outcome are high especially in subjects with underlying comorbidities (such as diabetes and chronic nephropathy).
In most people, however, MERS-CoV infection is manifested by fever, cough and difficulty breathing.
Although most MERS cases have arisen in Saudi Arabia and the United Arab Emirates, cases have also been reported in Europe, the United States and Asia in people who have traveled - or who have had contact with those who have gone - in Middle East.
Dromedaries and camels are implicated in direct or indirect transmission to humans, although the exact mode of transmission has not yet been confirmed. The inter-human contagion appears limited and appears to occur mainly through droplets of saliva (droplets) or by direct contact.
At the moment, there is no specific pharmacological treatment for MERS and hygiene measures to prevent the spread of infection are crucial. The understanding of the virus and the disease it causes is constantly evolving.
Characteristics of the virus
The Middle Eastern respiratory syndrome is caused by a virus belonging to the large family of Coronavirus, called MERS-CoV (acronym of "Middle East Respiratory Syndrome Coronavirus").
Initially called N-CoV (New Corona Virus), this viral agent was identified for the first time on September 24, 2012, in Saudi Arabia, by the Egyptian virologist Ali Mohamed Zaki, who had been subjected to the case of a 60-year-old who died for a severe and mysterious form of pneumonia.
The MERS virus (MERS-CoV) isolated from this patient had characteristics similar to that of acute respiratory syndrome (SARS-CoV).
MERS-CoV is a single-stranded, positive-sense RNA virus.
The genomic sequence indicates that MERS-CoV is closely related to some Coronavirus of bats (hence the hypothesis that these animals could represent the natural reservoir of infection).
What are Coronaviruses?
These are viruses detected for the first time in the sixties. Their name derives from the characteristic "crown" shape visible on the electron microscope.
These microorganisms cause respiratory infections in both humans and animals. Some Coronaviruses cause trivial colds and mild infections of the respiratory tract, others are responsible for severe lung disorders, as in the case of SARS (infectious pneumonia that broke out in China in 2002, infecting eight thousand people and killing almost eight hundred).
MERS and SARS: Differences
Middle Eastern respiratory syndrome has been called the "new SARS".
In reality, the MERS-CoV, despite being distantly related to the Coronavirus that causes acute respiratory syndrome (belonging to the same family of viruses), presents significant differences.
On the basis of current information, in fact, it seems that MERS-CoV is transmitted less easily among people than the SARS virus, but is able to cause a more serious form of disease that correlates to a higher mortality rate (due to the death in approximately 30-40% of cases, compared with 10% of acute severe respiratory syndrome).
Contagion
The mode of transmission of MERS-CoV has not yet been confirmed, however it seems possible the inter-human infection by respiratory route and by direct contact with infected camelids.
At the moment, investigations are underway to determine the source of the virus and the dynamics with which it has come to infect humans.
Transmission from animals to humans
So far, the hypotheses attribute to camels and dromedaries the role of human infection vehicles, as the genetic sequences examined show a close link between the virus found in these animals and the one that infects people in the same geographical area (Arabia Saudi, Qatar, Oman and Egypt).
The natural reservoir of the infection, instead, would be represented by the bats.
Transmission from person to person
Human-to-human transmission is possible. This mode of inter-human contagion, however, does not seem to be firmly supported in all cases of illness. For this reason, it is considered possible the presence within the communities of "super-spreader" individuals, capable of spreading the infection more rapidly than others.
However, it must still be established definitively whether the virus is contracted by air (through respiratory particles emitted with coughing or sneezing) or by prolonged contact with infected persons or objects contaminated by them.
Geographical distribution
So far, most MERS cases have occurred in countries of the Arabian peninsula.
From Saudi Arabia, the MERS has spread to neighboring Middle Eastern countries, affecting Jordan, Qatar and the United Arab Emirates with small epidemic outbreaks.
Since its discovery in 2012, MERS-CoV infections have also been reported in Lebanon, Kuwait, Oman, Yemen, Algeria, Iran, Egypt, Tunisia, the Philippines and Malaysia.
The sporadic cases reported in Europe (France, Germany, Italy, the United Kingdom, the Netherlands and Greece) and in non-European countries (United States) concern people who have traveled to the Middle East or who have had close contact with travelers from these areas.
The first Italian case was reported on May 31, 2013 in Tuscany. Although there is little chance of infection in Europe, the import of the virus from high-risk countries, such as the Arabian Peninsula, remains possible.
Situations more at risk
Particular concern is the annual pilgrimage to Mecca, on the occasion of Ramadan, which could facilitate the further spread of Coronavirus, given the migration of thousands of faithful to and from Saudi Arabia (the country where the epidemic broke out) and where the greatest number of deaths is recorded to date).
The first cases in South Korea
Since May 20, 2015, an outbreak of MERS in South Korea has been notified to WHO, which has reached worrying data. As of June 10, 2015, 107 human cases of infection and nine deaths were confirmed. The "zero patient" is a 68-year-old man who returned to South Korea after a trip to the Arabian Peninsula. In fact, the genome of the virus that is spreading in South Korea has been sequenced and proved to be the same as that circulating in the countries of the Middle East.
Incubation period
Based on the information we have collected so far, the incubation period for middle-eastern respiratory syndrome is 5-6 days, but can vary from 2 to 14 days.
MERS presents itself with a wide range of clinical manifestations: in some cases, it can be asymptomatic or give rise to slight disorders; in others, it can cause acute respiratory distress syndrome and multi-organ failure.
Almost all symptomatic patients have difficulty breathing.
MERS is associated with high mortality in patients with comorbid disorders, such as diabetes and kidney failure.
Symptoms
MERS-CoV infection generally presents itself as a sort of flu-like syndrome, with fever, chills, headache, muscle pain, arthralgia and generalized malaise.
After about 7 days, however, the symptoms worsen and dry cough and difficulty breathing, which rapidly progress to pneumonia in most patients. In some cases, the virus also causes gastrointestinal disorders (abdominal pain, diarrhea, nausea and / or vomiting) and can lead to kidney failure or septic shock.
In people suffering from chronic diseases (diabetes, nephropathy, cancer and lung diseases), the Middle Eastern respiratory syndrome can complicate into a severe acute respiratory failure and lead to death. At risk of fatal outcome are the elderly and the immunosuppressed, in whom the disease may have an atypical presentation.
Period of contagiousness
The period of infectiousness, due to MERS-CoV infection, is unknown.
The greatest danger of infection is achieved by staying in close contact with a patient in the acute phase. During an epidemic, most cases are the result of human-to-human transmission in the health sector, especially when prevention and infection control measures are inadequate.
Diagnosis
- People with breathing difficulties and discomfort in the 14 days following the return from a trip to the Middle East should consult their doctor.
- It is not always possible to immediately identify patients with MERS because, as with other respiratory infections, the first symptoms are non-specific. Pneumonia is a common finding in the examination, but it is not always present.
- The diagnosis of MERS is established mainly through serological tests and isolation of the virus by PCR (polymerase chain reaction) techniques on respiratory samples.
- Serological tests that determine whether a person has been infected with the MERS-CoV virus and developed an immune response include three separate tests: ELISA or enzyme-linked immunosorbent (screening test), IFA or immunofluorescent dosage (confirmation test ) and dosage of neutralizing antibodies (slowest but definitive confirmation test).
Treatment
There are no specific antiviral therapies for MERS, but some pharmacological approaches are being evaluated.
At the moment, the treatment is supportive and is established based on the patient's clinical conditions. MERS-CoV pneumonia can rapidly evolve into acute respiratory failure, which requires mechanical ventilation and medical care to maintain vital organ functions.
Is there a vaccine?
Currently, a vaccine is not available to prevent MERS-CoV infection.
Prevention
For travelers traveling to or from endemic areas, the WHO recommends following general hygiene measures implemented to control other respiratory infections at risk of pandemic epidemics.
Based on the current situation and available information, in particular, we encourage:
- Wash hands frequently with soap and water (or alcoholic solutions);
- If your hands are dirty, try not to touch your eyes, nose or mouth;
- Respect a good respiratory hygiene, such as sneezing or coughing in a handkerchief or with the elbow flexed, use a mask and throw the used tissues in a closed basket immediately after use;
- Avoid close contact with anyone who shows the symptoms of the disease (cough and sneeze) or with potentially infected animals (in particular, camelids);
- Avoid eating raw or undercooked meat;
- Consume fruit and vegetables only if properly washed;
- Avoid drinking unpasteurized milk and non-bottled beverages.
To reduce the risk of contracting the infection, the World Health Organization calls not to drink raw milk or camel urine. People visiting farms, markets or other places where animals are present should avoid unnecessary contact with bats, camels or camels.
In endemic areas, breeders and butchers should remember to wash their hands before and after touching camels and other animals, protect their faces and, when possible, use protective clothing, which must be removed and washed at the end of each working day.
Sick animals should never be slaughtered for consumption.
Risks for travelers
The Centers for Disease Prevention and Control (CDC) and the World Health Organization are closely monitoring the virus.
Currently, there is no restriction on travel in the Middle East or other places where the presence of the virus has been reported.
Pandemic risk
According to the World Health Organization, the Middle Eastern respiratory syndrome is not yet an international health emergency, but a disease to be kept under strict surveillance.
As of 31 May 2015, 1180 human MERS-CoV infection cases confirmed in the laboratory were reported to the World Health Organization (WHO) (483 deaths; 40% mortality).
MERS-CoV continues to be an endemic threat to low-level public health. However, the possibility that the virus may mutate could result in greater inter-human transmissibility, a factor that could increase its pandemic potential.
