Various news sources today report that dromedary camels – "ships of the desert" as The Independent puts it – could be the source of the MERS (Middle East respiratory syndrome) virus that emerged last year. MERS is believed to be caused by a type of coronavirus.
Coronaviruses are found worldwide and cause respiratory illnesses of varying severity, ranging from the common cold to the severe respiratory illness SARS.
As of August 2013, there have been 94 confirmed cases of MERS, all in people with links to Jordan, Qatar, Saudi Arabia and the United Arab Emirates.
There has been some evidence of human-to-human transmission of MERS, but it is thought that the virus could have been spread through contact with animals. Animals are common "biological reservoirs" for coronaviruses.
In the current study, blood samples routinely collected from a group of camels in Oman were all found to be positive for antibodies against MERS virus, suggesting that the animals had been infected with the virus. Only 9% of samples from camels in the Canary Islands were positive for antibodies against MERS virus.
The researchers say that this does not mean that camels are necessarily the main animal reservoirs – they have not yet tested other livestock from the Middle East where MERS has occurred. Even if camels are the main reservoir for infection it remains unclear what level of contact with them could cause transmission.
WHO has been informed of six additional laboratory-confirmed cases of infection with Middle East respiratory syndrome coronavirus (MERS-CoV). Of these, two cases have been reported from Saudi Arabia and four from the United Arab Emirates (UAE).
Both the cases in Saudi Arabia have mild symptoms and are not hospitalized. They are from Asir region. The first case is a 26-year-old man who is a close contact with a previously laboratory-confirmed case and the second case is a 42-year-old woman who is a health care worker.
In the UAE, the four cases are health care workers from two hospitals in Abu Dhabi who took care of an earlier laboratory-confirmed patient. Of these, two cases, a 28-year-old man and 30-year-old woman, did not develop symptoms of illness. The other two cases, both women of 30 and 40 years old, had mild upper respiratory symptoms and are in stable condition.
Globally, from September 2012 to date, WHO has been informed of a total of 88 laboratory-confirmed cases of infection with MERS-CoV, including 45 deaths.
Based on the current situation and available information, WHO encourages all Member States to continue their surveillance for severe acute respiratory infections (SARI) and to carefully review any unusual patterns.
Health care providers are advised to maintain vigilance. Recent travelers returning from the Middle East who develop SARI should be tested for MERS-CoV as advised in the current surveillance recommendations.
Specimens from patients’ lower respiratory tracts should be obtained for diagnosis where possible. Clinicians are reminded that MERS-CoV infection should be considered even with atypical signs and symptoms, such as diarrhea, in patients who are immunocompromised.
Health care facilities are reminded of the importance of systematic implementation of infection prevention and control (IPC). Health care facilities that provide care for patients suspected or confirmed with MERS-CoV infection should take appropriate measures to decrease the risk of transmission of the virus to other patients, health care workers and visitors.
All Member States are reminded to promptly assess and notify WHO of any new case of infection with MERS-CoV, along with information about potential exposures that may have resulted in infection and a description of the clinical course. Investigation into the source of exposure should promptly be initiated to identify the mode of exposure, so that further transmission of the virus can be prevented.
WHO does not advise special screening at points of entry with regard to this event nor does it currently recommend the application of any travel or trade restrictions.
WHO has convened an Emergency Committee under the International Health Regulations (IHR) to advise the Director-General on the status of the current situation. The Emergency Committee, which comprises international experts from all WHO Regions, unanimously advised that, with the information now available, and using a risk-assessment approach, the conditions for a Public Health Emergency of International Concern (PHEIC) have not at present been met.
Coronaviruses are species in the genera of virus belonging to the subfamily Coronavirinae in the family Coronaviridae. Coronaviruses are enveloped viruses with a positive-sense RNA genome and with a nucleocapsid of helical symmetry. The genomic size of coronaviruses ranges from approximately 26 to 32 kilobases, extraordinarily large for an RNA virus. The name "coronavirus" is derived from the Latin corona, meaning crown or halo, and refers to the characteristic appearance of virions under electron microscopy (E.M.) with a fringe of large, bulbous surface projections creating an image reminiscent of the solar corona. This morphology is created by the viral spike (S) peplomers, which are proteins that populate the surface of the virus and determine host tropism. Coronaviruses are grouped in the order Nidovirales, named for the Latin nidus, meaning nest, as all viruses in this order produce a 3' co-terminal nested set of subgenomic mRNA's during infection.
Proteins that contribute to the overall structure of all coronaviruses are the spike (S), envelope (E), membrane (M) and nucleocapsid (N). In the specific case of the SARS coronavirus (see below), a defined receptor-binding domain on S mediates the attachment of the virus to its cellular receptor, angiotensin-converting enzyme 2 (ACE2). Some coronaviruses (specifically the members of Betacoronavirus subgroup A) also have a shorter spike-like protein called hemagglutinin esterase (HE).
Coronaviruses primarily infect the upper respiratory and gastrointestinal tract of mammals and birds. Four to five different currently known strains of coronaviruses infect humans. The most publicized human coronavirus, SARS-CoV which causes SARS, has a unique pathogenesis because it causes both upper and lower respiratory tract infections and can also cause gastroenteritis. Coronaviruses are believed to cause a significant percentage of all common colds in human adults. Coronaviruses cause colds in humans primarily in the winter and early spring seasons. The significance and economic impact of coronaviruses as causative agents of the common cold are hard to assess because, unlike rhinoviruses (another common cold virus), human coronaviruses are difficult to grow in the laboratory. Coronaviruses can even cause pneumonia, either direct viral pneumonia or a secondary bacterial pneumonia.
In chickens, the infectious bronchitis virus (IBV), a coronavirus, targets not only the respiratory tract but also the uro-genital tract. The virus can spread to different organs throughout the chicken.
Coronaviruses also cause a range of diseases in farm animals and domesticated pets, some of which can be serious and are a threat to the farming industry. Economically significant coronaviruses of farm animals include porcine coronavirus (transmissible gastroenteritis coronavirus, TGE) and bovine coronavirus, which both result in diarrhea in young animals. Feline Coronavirus: two forms, Feline enteric coronavirus is a pathogen of minor clinical significance, but spontaneous mutation of this virus can result in feline infectious peritonitis (FIP), a disease associated with high mortality. There are two types of canine coronavirus (CCoV), one that causes mild gastrointestinal disease and one that has been found to cause respiratory disease. Mouse hepatitis virus (MHV) is a coronavirus that causes an epidemic murine illness with high mortality, especially among colonies of laboratory mice. Prior to the discovery of SARS-CoV, MHV had been the best-studied coronavirus both in vivo and in vitro as well as at the molecular level. Some strains of MHV cause a progressive demyelinating encephalitis in mice which has been used as a murine model for multiple sclerosis. Significant research efforts have been focused on elucidating the viral pathogenesis of these animal coronaviruses, especially by virologists interested in veterinary and zoonotic diseases.
Replication of Coronavirus begins with entry to the cell which takes place in the cytoplasm in a membrane-protected microenvironment. Upon entry to the cell the virus particle is uncoated and the RNA genome is deposited into the cytoplasm. The Coronavirus genome has a 5’ methylated cap and a 3’polyadenylated tail. This also allows the RNA to attach to ribosomes for translation. Coronaviruses also have a protein known as a replicase encoded in its genome which allows the RNA viral genome to be transcribed into new RNA copies using the host cells machinery. The replicase is the first protein to be made as once the gene encoding the replicase is translated the translation is stopped by a stop codon. This is known as a nested transcript, where the transcript only encodes one gene—it is monocistronic. The RNA genome is replicated and a long polyprotein is formed, where all of the proteins are attached. Coronaviruses have a non-structural protein called a protease which is able to separate the proteins in the chain. This is a form of genetic economy for the virus allowing it to encode the greatest number of genes in a small number of nucleotides.
Coronavirus transcription involves a discontinuous RNA synthesis (template switch) during the extension of a negative copy of the subgenomic mRNAs. Basepairing during transcription is a requirement. Coronavirus N protein is required for coronavirus RNA synthesis, and has RNA chaperone activity that may be involved in template switch. Both viral and cellular proteins are required for replication and transcription. Coronaviruses initiate translation by cap-dependent and cap-independent mechanisms. Cell macromolecular synthesis may be controlled after Coronavirus infection by locating some virus proteins in the host cell nucleus. Infection by different coronaviruses cause in the host alteration in the transcription and translation patterns, in the cell cycle, the cytoskeleton, apoptosis and coagulation pathways, inflammation, and immune and stress responses.
In 2003, following the outbreak of Severe acute respiratory syndrome (SARS) which had begun the prior year in Asia, and secondary cases elsewhere in the world, the World Health Organization issued a press release stating that a novel coronavirus identified by a number of laboratories was the causative agent for SARS. The virus was officially named the SARS coronavirus (SARS-CoV).
The epidemic resulted in over 8,000 infections, about 10% of which resulted in death. X-ray crystallography studies performed at the Advanced Light Source of Lawrence Berkeley National Laboratory have begun to give hope of a vaccine against the disease "since [the spike protein] appears to be recognized by the immune system of the host."
Following the high-profile publicity of SARS outbreaks, there has been a renewed interest in coronaviruses among virologists. For many years, scientists knew about only two human coronaviruses (HCoV-229E and HCoV-OC43). The discovery of SARS-CoV added a third human coronavirus.
By the end of 2004, three independent research labs reported the discovery of a fourth human coronavirus. It has been named NL63, NL, and the New Haven coronavirus by different research groups. The three labs are still arguing over which one discovered the virus first and has the right to name it.
Early in 2005, a research team at the University of Hong Kong reported finding a fifth human coronavirus in two patients with pneumonia. They named it Human coronavirus HKU1.
In September 2012, what is believed to be a sixth new type of coronavirus, tentatively referred to as Novel Coronavirus 2012, being like SARS (but still distinct from it and from the common-cold coronavirus) was discovered in Qatar and Saudi Arabia. The World Health Organisation has accordingly issued a global alert and an interim case definition to help countries to strengthen health protection measures against it. The WHO update on 28 September 2012 said that the virus did not seem to pass easily from person to person. However, on May 12, 2013, a case of contamination from human to human in France was confirmed by the French Ministry of Social Affairs and Health. In addition, cases of person-to-person transmission have been reported by the Ministry of Health in Tunisia. Two confirmed cases seem to have caught the disease from their late father, who became ill after a visit to Qatar and Saudi Arabia. So far there have been twenty-two cases and ten deaths in eastern Saudi Arabia. After the Dutch Erasmus Medical Centre sequenced the virus, the virus was given a new name, Human Corona Virus-Erasmus Medical Centre (HCoV-EMC). The final name for the virus is: Middle East respiratory syndrome coronavirus (MERS-CoV)
- Human coronavirus 229E
- Human coronavirus OC43
- Human Coronavirus NL63 (HCoV-NL63, New Haven coronavirus)
- Human coronavirus HKU1
- Middle East respiratory syndrome coronavirus (MERS-CoV), previously known as Novel coronavirus 2012 and HCoV-EMC.
- Coronaviruses have been recognized as causing pathological conditions in veterinary medicine since the early 1970s. Except for avian infectious bronchitis, the major related diseases have mainly an intestinal location.
- (listed following their estimated economical importance)
- Infectious bronchitis virus (IBV) causes avian infectious bronchitis.
- Porcine coronavirus (transmissible gastroenteritis coronavirus of pigs, TGEV).
- Bovine coronavirus (BCV), responsible for severe profuse enteritis in of young calves.
- Feline coronavirus (FCoV) causes mild enteritis in cats as well as severe Feline infectious peritonitis (other variants of the same virus).
- the two types of canine coronavirus (CCoV) (one causing enteritis, the other found in respiratory diseases).
- Turkey coronavirus (TCV) causes enteritis in turkeys.
- Ferret enteric coronavirus causes epizootic catarrhal enteritis in ferrets.
Indian authorities are finally waking up to the dangers of MERS-CoV. Dr Ram Shukla, a specialist in infectious diseases from the UAE tells us 12 important facts about the disease:1. Spread by animals in contact with batsMostly carried by bats but also some other vertebrates, the MERS Coronovirus spreads very rapidly in animals when they are kept together in confined and crowded places like live-animal markets, slaughter houses and while transporting animals by ships. Close and prolong contact with infected animals, which may not show any symptoms, helps virus jump to human. As it happened in SARS most of the animal traders were found to have SARS antibodies without any symptoms. This is a stage of adaptation to a new host (Inter-species transfer) which led to possible viral genetic mutation to adapt to its new human host. Same may be true for MERS-CoV.2. It doesn’t spread rapidly among humansMERS is not transmitted very readily from person-to-person. This may occur after close and prolonged contact with infected patient in closed environment like home, hospitals etc. Infection spreads by coughing, droplet infection. But it can become air borne, meaning spread by air in hospitals when infected patient is given pressurized oxygen, intubated or procedures like bronchoscopy or during the use of pressurized devises like dental drill etc making healthcare workers more susceptible.3. Infection control in hospitals and clinics can prevent spreadHealthcare workers getting infected by MERS are reported on a regular basis which shows failure of observing stringent Infection Control Procedures in the hospitals. It is the responsibility of the hospitals to educate their staff, supervise and implement strict Infection Control and isolation procedures. Infected healthcare workers take the infection to their family and wider community.4. Masks and other physical barriers will not helpCasual contact in open spaces is unlikely to transmit the virus. Using face masks or other such physical barriers is not of much benefit. But it is wise to observe meticulous hand hygiene by soap and water or hand alcohol rub. (Read: Lessons from the SARS chapter which will help us fight)5. Simple measures can prevent spreadInfected patient spreads it by coughing out the virus particles known as droplet infection. These droplets spread to the distance of one to one and half meters. If patient does not cover his mouth, this may infect furniture, door knobs, lift buttons etc for few hours depending upon the environmental temperature, humidity, air flow etc. Hence, it is highly advised that good cough-etiquette be observed, meticulous hand hygiene should be maintained and contaminated surfaces be disinfected.6. It takes 7-10 days for symptoms to developThe long incubation period of MERS is good news. This helps public health authorities to identify those who may have got infected (contact tracing). These individuals are observed, isolated or quarantined, so as to break the chain of transmission.7. The symptoms may not all be respiratoryEven though the most common symptoms are fever, cough and difficulty in breathing, it can also lead to kidney failure, septic shock, multi-organ failure and acute respiratory failure. These are usually the cause for the high death rate, nearly 60% (death rate of SARS was 8%).8. The virus may not really affect the upper respiratory tractThe MERS virus enters by nose or mouth and uses certain receptors to enter human cells. These receptors are common in the lower respiratory tract but not in the upper respiratory tract – that is why the virus causes illness in the lungs (pneumonia) rather than in the nose and throat as a cold virus or H1N1 would. These receptors are found in kidney too causing renal failure. So if we block these receptors by drugs, we can prevent infection by MERS. Even though certain anti-diabetic drugs are also known blockers of the same receptors, scientists have found that these drugs are not useful in blocking MERS virus. They hope to develop a drug or a vaccine to block the receptor to prevent MERS infection.9. Improving your immunity could prevent the diseaseAll available cases data indicate that the people who are susceptible include those who are very old, very young, pregnant women, individuals with compromised immune system due to diseases, drugs and organ transplant patients. Young and healthy healthcare workers get infected in hospital settings because of the prolonged close contact with infected patients.10. PCR tests can help diagnose MERS-CoVThere is a sophisticated test like PCR to diagnose it but this is only available in specialized laboratories. There is no quick test. There is no specific drug or treatment for MERS but only supportive treatment given in the hospital.11. MERS-CoV cannot spread very fastSo far it fails to show epidemic potential. It is not easily transmissible from person to person. Its receptor is deep in the lungs so requires prolonged close contact with the infected patient. It has a long incubation period which makes public health interventions like contact tracing and isolation effective.12. Screening at airports could help
- Genus Gammacoronavirus; type species: Avian coronavirus
Gulf sector is a very busy sector as millions of Indians are working in the Gulf countries. On top of that 1.7 million Indians will perform Haj this year. Airport screening is one of the methods to detect cases with fever by installing thermal scans or by manual methods. Education of travellers about the disease; explaining risks of getting infected, how to maintain good hygiene and what to do if symptoms develop after returning back home could also help. (Read: The MERS-CoV timeline)
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