What is Middle East Respiratory Syndrome?
The Middle East respiratory syndrome (MERS), or what is known as camel flu, is a respiratory infection caused by MERS-coronavirus (MERS-CoV). MERS was first reported in 2012. There are around 1641 confirmed cases of MERS in about 20 countries as updated in December 2015. The existence of this virus was first reported by Dr. Ali Mohamed Zaki an Egyptian virologist, in the year 2012. A previously unknown coronavirus was isolated by Dr. Zaki from a man’s lungs. This was later identified as MERS-CoV. The symptoms are not fatal unless the infected person has a weakened state of immunity due to other health problems. The symptoms include fever, cough, diarrhea, and shortness of breath.
In the very same year, the similar symptoms were observed in a 49-year-old male in Qatar. Most of the MERS cases which were observed were confined to Arabian Peninsula. There were, however, two cases reported in California. Two healthcare providers who treated people in Saudi Arabia were infected with the virus. This outbreak led to the rapid research and monitoring on the symptoms and the deaths associated with this virus. The first two cases had similarities in the genetic sequences.
MERS-CoV is a beta coronavirus which is derived from bats. Serum isolated from camels have the antibodies for MERS-CoV. However, the source of the infection has not been identified in camels. It is also believed that the camels transfer the virus to humans, but, the exact mechanism is unknown. Human-human transmission is on close contact. The mortality rate is 40%.
Symptoms of MERS
The appearance of the symptoms is after an incubation period of 5 days. Fever, cough, and shortness of breath are the most common symptoms. Myalgia is one of the symptoms observed in a small fraction of people. Apart from these symptoms, gastrointestinal symptoms like vomiting, diarrhea, and abdominal pain are also seen in a small fraction of people. Three-quarters of the total number of people infected need medical attention and support of ventilators to survive. Though the symptoms appear non-fatal, MERS can be asymptomatic and lead to severe pneumonia which in turns causes Acute Respiratory Distress Syndrome (ARDS). It can also further complicate by causing kidney failure, disseminated intravascular coagulation (DIC), and pericarditis.
More about MERS-CoV
MERS-CoV belongs to the beta group of coronavirus. Though it was referred to as SARS-like virus until 2013, it has now been identified to be distinct from SARS coronavirus.
In humans, the adherence of the virus is to the nonciliated bronchial epithelial cells. The virus is equipped to evade the immune system and they hinder the production of the interferon (IFN) production in these cells. The reason this is unique is because most respiratory disease causing viruses have a strong tropism for ciliated cells. Dipeptidyl peptidase 4 (DPP4) or CD26 is the receptor for the virus. This receptor is highly conserved and only expressed in human bronchial epithelium and the kidneys.
Transmission between human-human is very low unless the person infected is in constant contact with healthy individuals. It has also been observed that only 20% of the epithelial cells are infected with the virus on a whole. This indicates that the number of virions which have to be inhaled to cause the disease will not likely transfer from human-human through normal contact. However, Dr. Anthony S. Fauci of the National Institutes of Health in Bethesda, Maryland, has raised a cause for concern. The infection though does not transmit from human-human, its mutation to a more transmissible strain can pose a major health hazard. Healthcare providers are exposed the most to this virus. The major outbreak in South Korea with 125 confirmed cases of MERS has CDC on high alert. Egyptian tomb bats are the natural reservoirs of this virus. The virus has undergone evolution over a long period of time. The viral strains in bats are similar to the ones isolated from humans. Nevertheless, recent reports have identified camels to be the natural reservoirs of the virus. The presence of protein-specific antibodies against MERS-CoV spike proteins are in evidence of this. Countries in the Arabian Peninsula are known to drink large amounts of camel milk and camel meat as well. This is one of the main reasons for the transmission of the virus.
Diagnosis of MERS
The diagnosis of the disease is based on the symptoms displayed by an individual. The probable cases of MERS show the following symptoms: acute pneumonia, flu-like symptoms, fever, and cough, a history of travel to other countries, contact with an infected person or consumption of camel products.
X-ray of the lungs reveals bilateral patchy infiltrates which is consistent with viral pneumonitis and ARDS. Interstitial infiltrates are also seen.
Low lymphocyte count is characteristic of this disease. PCR is performed by taking samples from the lower respiratory tract. Sputum sample or tracheal aspirate is also taken for examination. RT-PCR is also performed for the rapid identification of the infection. The PCR targets the amplification of sequence upstream the E gene. RdRp, which is present in all coronaviruses is targeted by sequencing amplicons.
Though immunofluorescence assays have been developed, the antibodies cross-react within the genus and thus make it difficult to detect the infection. A protein microarray specific to the infection has been developed. There was no cross-reactivity observed. However, the assay is tedious which is why WHO came up with the conclusion that all the positive serological test results in the absence of PCR and other sequencing techniques are to be taken as probable cases of MERS.
Prevention of MERS
For any infection, the transmission matters the most. Once the transmission is prevented, the infection is automatically controlled.
1. Camel milk should be thoroughly pasteurized before consumption and camel meat too should be cooked well prior to consumption.
2. People handling camels should wash their hands clean after coming in contact with them. The same way, unwell camels should be given proper medical attention and should be kept away from the healthy ones to prevent the spread of the infection.
3. Protective gear should be worn by healthcare providers while treating infected individuals.
4. Handling body fluids with care is advised.
5. Wearing long gowns which are impermeable and non-sterile is mandatory.
6. Only a limited number of people should be allowed to care for the patient.
7. The patient is advised to limit activity to a bare minimum to avoid contamination of surfaces at home or hospital.
Treatment of MERS
Interferon activity is hindered by the virus. To counter this, treatment procedure involves administration of exogenous interferons which minimize the viral replication process. There is no specific antiviral treatment. The treatment is mostly symptomatic and in severe cases, the patients are provided care to keep the vital organs functioning.