Middle East respiratory syndrome coronavirus (MERS-CoV) summary and literature update – as of 13 August 2013
Since April 2012, 94 laboratory-confirmed and 16 probable cases of human infection with Middle East respiratory syndrome coronavirus (MERS-CoV) have been reported to WHO. Affected countries in the Middle East include Jordan, Saudi Arabia (KSA), the United Arab Emirates (UAE), and Qatar; in Europe countries affected include: France, Germany, the United Kingdom (UK) and Italy; and in North Africa: Tunisia. Infections presumably acquired through exposure to non-human sources have all occurred in the Middle East; limited transmission in the countries of Europe and North Africa has occurred in close contacts of recent travelers from the Middle East. No new countries have reported MERS-CoV cases since the last update; the last exported case to a country outside the Middle East was in June 2013.
Since the last update, 15 new laboratory-confirmed cases of MERS-CoV were reported by KSA and UAE, bringing the total to 94 cases. Forty-seven (50%) of these have died. Fifty-five of 90 confirmed cases (61%) for which the sex is known were male, and the median age of the confirmed cases with known age (n=89) is 50 years (range, 14 months to 94 years).
Two small clusters have been reported since the last update. One cluster occurred in a health care setting in UAE. The index case was an 83-year-old UAE resident without history of travel or contact with other confirmed cases. He had an underlying malignant disease and was hospitalized in Abu Dhabi with respiratory symptoms on 6 July 2013. He was noted to own a farm with a variety of animals, which he visited often. He tested positive for MERS-CoV in lower and upper respiratory tract samples on 10 July. His condition deteriorated and he developed the acute respiratory distress syndrome and died. Although infection prevention and control measures were reported to be in place and the patient was isolated, four secondary cases were reported in health care workers with exposure to the patient. Two of them developed a mild disease and the other two remained asymptomatic.
Two cases were reported in the Asir region of Saudi Arabia; both of these had previous contact with a confirmed case. The index case in this cluster was thought to be a 66-year-old male from Asir with an underlying medical condition who died of MERS-CoV infection. One secondary case is a male family member, 26 years of age, and the other secondary case is a 42-year-old health care worker. Both experienced mild disease, with no hospitalization required.
For further details regarding the cases please refer to:
WHO MERS-CoV related activities and upcoming guidance
WHO is currently coordinating the collection of a panel of clinical serum specimens, which will include both positive and negative MERS-CoV specimens, to standardize serological assays. This is in collaboration with an international network of public health and research laboratories.
Recent WHO published guidelines
On 25 July 2013, WHO published travel advice on MERS-CoV for pilgrimages to minimize the risk of MERS-CoV infection in pilgrims and other travellers. It covers recommendations for effective communication of risk information and guidance on actions before, during and after pilgrimages.
On 30 July 2013, WHO published a questionnaire for an initial interview of cases of MERS-CoV infection as a supplemental tool to accompany the WHO guidelines for investigation of cases of human infection with MERS-CoV. It is designed to gather initial information about the potential exposures of cases of MERS-CoV infection 14 days before symptom onset. It will assist investigators in developing hypotheses about possible sources and exposure during subsequent formal studies.
On 8 August 2013, recommendations were published on infection prevention for patients being cared for at home. These recommendations are informed by evidence-based guidelines, and are focused particularly on patients with MERS-CoV infection presenting with mild symptoms and asymptomatic contacts.
Rapid advice note on home care for patients with Middle East respiratory syndrome coronavirus (MERS-CoV) infecti on presenting with mild symptoms and management of contacts
On 9 August 2013, frequently asked questions on MERS-CoV were updated to reflect findings from recent publications, including a recent report of MERS-CoV reactive antibodies in camels (cited below).
Recent peer-reviewed literature
Several scientific investigations have been published in peer-reviewed journals since the last update:
French investigators explored the pandemic potential of MERS-CoV. They considered two scenarios with different basic reproduction numbers (R0) and concluded that MERS does not yet have pandemic potential.
Reference: Romulus Breban, Julien Riou, Arnaud Fontanet: Interhuman transmissibility of Middle East respiratory syndrome coronavirus: estimation of pandemic risk. The Lancet, 05 July 2013 (Article in Press DOI: 10.1016/S0140-6736(13)61492-0)
Sera from camels in the Canary Islands and Oman have been found to be positive for MERS-CoV spike protein-specific antibodies. The sera were collected for routine veterinary surveillance of camels from mid-2012 to mid-2013. One hundred percent of sera tested from 50 female Omani racing camels and 14.3% (15/105) of the Spanish camels were found to have MERS-CoV spike protein-specific antibodies. This study suggests that MERS-CoV or MERS-CoV-related virus has infected camel populations, and may have been widely circulating among camels in Oman.
Reference: Reusken et al.: Middle East respiratory syndrome coronavirus neutralising serum antibodies in dromedary camels: a comparative serological study. The Lancet Infectious Diseases, 09 August 2013 (Article in Press DOI: 10.1016/S1473-3099(13)70164-6)
The Saudi Arabian Ministry of Health provided an analysis of 47 individuals with laboratory-confirmed MERS-CoV disease reported between 1 September 2012 and 15 June 15 2013, which included cases from the Al-Hasa hospital outbreak. The male: female case ratio was 3.3:1, with a case-fatality rate of 60%. Of the confirmed cases 96% had underlying comorbidities. The mortality rate for patients with comorbidities was high (60%).
Reference: Assiri et al.: Epidemiological, demographic, and clinical characteristics of 47 cases of Middle East respiratory syndrome coronavirus disease from Saudi Arabia: a descriptive study. The Lancet Infectious Diseases, 26 July 2013 (Article in Press DOI: 10.1016/S1473-3099(13)70204-4)
Worldwide flight itinerary data and historic hajj pilgrim data from 2012 were analyzed to predict population movements out of Saudi Arabia and the Middle East and potential for worldwide spread of MERS-CoV. An estimated 65.1% of the foreign pilgrims were from low- and lower-middle income countries. Authors highlighted that the results could be useful to guide and focus surveillance and preparedness efforts in the relevant countries.
Reference: Khan et al.: Potential for the international spread of Middle East respiratory syndrome in association with mass gatherings in Saudi Arabia. PLOS Currents Outbreaks, 2013 Jul 17 [last modified: 2013 Jul 17]. Edition 1. doi: 10.1371/currents.outbreaks.a7b70897ac2fa4f79b59f90d24c860b8.
Although new cases continue to occur in the Arabian Peninsula, no new exported cases have been reported since June despite a surge in pilgrims to Saudi Arabia to perform Umra during Ramadan. The KSA Ministry of Health also reports finding no MERS-CoV infections among pilgrims during their enhanced surveillance activities. However, as Ramadan ended on 8 August and the incubation period for MERS-CoV can be as long as 10 days or more, continued vigilance is suggested. It is notable that only one previously reported case became ill after a pilgrimage.
As case finding and contact tracing around cases increases, increasing numbers of secondary cases with mild disease have been reported, indicating a broader spectrum of disease than previously recognized. However, transmission continues to be limited in clusters and does not appear to be extending into the wider community. Although the pattern may be changing slightly, index and sporadic cases, that is, those presumed to have non-human exposures as a source of their infections, continue to be older and are more likely to be male than secondary cases.
While the recent report by Reusken et al. may provide a clue as to a potential source of human infection, it is important to definitively demonstrate the presence of MERS virus in camels to confirm that the virus producing the antibody response is the same as that seen in humans. It is also important to note that the study involved only camels from Oman; other species were not available for testing and as such it is premature to focus solely on camels as a potential source of infection in humans. The critical question that remains to be answered is what exposures and activities in humans place them in contact with the virus and result in infection. This question needs to be answered urgently to inform measures that will prevent transmission to humans. This study, and the demographic differences noted above in cases acquiring infection from non-human exposures, may help to guide future investigations.
WHO provides guidance and tools for carrying out investigations into human cases of MERS-CoV.
WHO guidelines for investigation of cases of human infection with Middle East Respiratory Syndrome Coronavirus (MERS-CoV)
Middle East Respiratory Syndrome Coronavirus (MERS-CoV) Initial Interview Questionnaire of Cases
Case-control study to assess potential risk factors related to human illness caused by Middle East Respiratory Syndrome Coronavirus (MERS-CoV)
WHO continues to request that Member States report all confirmed and probable cases along with information about their exposures, testing, and clinical course to inform the most effective international preparedness and response. WHO strongly recommends detailed case investigations for every case, case-control studies for index cases and intensive follow up of contacts with serological testing to improve knowledge of the critical features of MERS-CoV infection.