Outbreak at a glance
From 29 December 2021 to 31 October 2022, four laboratory-confirmed cases of Middle East respiratory syndrome coronavirus (MERS-CoV) were reported to WHO by the Ministry of Health of the Kingdom of Saudi Arabia. No deaths were reported. Household contacts for the four cases were followed-up by the Ministry of Health, and no secondary cases were identified. The notification of these cases reiterates the need for global awareness of MERS-CoV but does not change the overall risk assessment.
Description of the cases
Since the last Disease Outbreaks News on MERS-CoV in Saudi Arabia published on 7 April 2022, the IHR National Focal Point of the Kingdom of Saudi Arabia has reported four additional cases, with no associated deaths.
Between 29 December 2021 and 31 October 2022, four cases of locally acquired Middle East respiratory syndrome coronavirus (MERS-CoV) infection were reported from Riyadh (two cases), Gassim (one case), and Makka Al Mukarramah (one case) regions (Figure 1). Laboratory confirmation of the cases was performed by real-time polymerase chain reaction (RT-PCR).
All the cases were non-health-care workers, who presented with fever, cough, and shortness of breath, and had comorbidities. Three of the cases had a history of contact with dromedary camels and consumption of their raw milk in the 14 days prior to the onset of symptoms. Three of the cases were male and the overall age range is 23 to 74-year-old.
Since the first report of MERS-CoV in 2012, a total of 2600 cases with 935 associated deaths have been reported from 27 countries, in all six WHO regions. The majority of MERS-CoV cases (n=2193; 84%) resulting in 854 deaths, have been reported from the Kingdom of Saudi Arabia (Figure 2).
Figure 1. Geographical distribution of MERS-CoV cases between 29 December 2021 – 31 October 2022 by city and region, Saudi Arabia (n=4). 
Table 1. MERS-CoV cases reported between 29 December 2021 – 31 October 2022
Figure 2: Distribution of cases and deaths from MERS-CoV in Saudi Arabia from 2013 to 20221
Epidemiology of MERS-CoV
Middle East respiratory syndrome (MERS) is a viral respiratory infection caused by a coronavirus called Middle East respiratory syndrome coronavirus (MERS-CoV). Approximately 36% of patients with MERS have died, but this may be an overestimate of the true mortality rate, as mild cases of MERS-CoV may be missed by existing surveillance systems, with case fatality rates counted only amongst the laboratory-confirmed cases.
Humans are infected with MERS-CoV from direct or indirect contact with dromedary camels who are the natural host and zoonotic source of the virus. MERS-CoV has demonstrated the ability to transmit between humans. So far, the observed non-sustained human-to-human transmission has occurred among close contacts and in healthcare settings. Outside of the healthcare setting, there has been limited human-to-human transmission.
MERS-CoV infections range from showing no symptoms (asymptomatic) or mild respiratory symptoms to severe acute respiratory disease and death. A typical presentation of MERS-CoV disease is fever, cough, and shortness of breath. Pneumonia is a common finding, but not always present. Gastrointestinal symptoms, including diarrhoea, have also been reported. Severe illness can cause respiratory failure that requires mechanical ventilation and support in an intensive care unit. The virus appears to cause more severe disease in older people, persons with weakened immune systems and those with comorbidities or chronic diseases such as renal disease, cancer, chronic lung disease, and diabetes.
No vaccine or specific treatment is currently available, although several MERS-CoV-specific vaccines and treatments are in development. Treatment is supportive and based on the patient’s clinical condition and symptoms.
Follow-up of the household contacts was conducted for all four cases, and no secondary cases were identified.
For the three cases reporting contact with camels, the Ministry of Agriculture was informed, and an investigation of camels was conducted. The identified positive camels were isolated.
The Ministry of Health of the Kingdom of Saudi Arabia is working to improve testing capacities for better detection of MERS-CoV during the ongoing COVID-19 pandemic.
Between September 2012 and 17 October 2022, the total number of laboratory-confirmed MERS-CoV infection cases reported globally to WHO is 2600 with 935 associated deaths. Most of these cases have occurred in countries in the Arabian Peninsula. There has been one large outbreak outside of the Middle East in May 2015, during which 186 laboratory-confirmed cases (185 in the Republic of Korea and 1 in China) and 38 deaths were reported, however, the index case in that outbreak had a travel history to the Middle East. The global number reflects the total number of laboratory-confirmed cases reported to WHO under IHR (2005) to date. The total number of deaths includes the deaths that WHO is aware of to date through follow-up with affected Member States.
The notification of the four cases does not change the overall risk assessment. WHO expects that additional cases of MERS-CoV infection will be reported from the Middle East and/or other countries where MERS-CoV is circulating in dromedaries, and that cases will continue to be exported to other countries by individuals who were exposed to the virus through contact with dromedaries or their products (for example, consumption of camel’s raw milk), or in a healthcare setting. WHO continues to monitor the epidemiological situation and conducts risk assessments based on the latest available information.
The number of MERS-CoV cases reported to WHO has substantially declined since the beginning of the ongoing COVID-19 pandemic. This is likely the result of epidemiological surveillance activities for COVID-19 being prioritized, resulting in reduced testing and detection of MERS-CoV cases. In addition, measures taken during the COVID-19 pandemic to reduce SARS-CoV-2 transmission (e.g. mask-wearing, hand hygiene, physical distancing, improving the ventilation of indoor spaces, respiratory etiquette, stay-at-home orders, reduced mobility) are also likely reduce opportunities for onward human-to-human transmission of MERS-CoV. However, the circulation of MERS-CoV in dromedary camels is not likely to have been impacted by these measures. Therefore, while the number of reported secondary cases of MERS has been reduced, the risk of zoonotic transmission remains.
Based on the current situation and available information, WHO re-emphasizes the importance of strong surveillance by all Member States for acute respiratory infections, including MERS-CoV, and to carefully investigate any unusual patterns.
Human-to-human transmission of MERS-CoV in healthcare settings has been associated with delays in recognizing the early symptoms of MERS-CoV infection, slow triage of suspected cases and delays in implementing infection, prevention and control (IPC) measures. IPC measures are therefore critical to prevent the possible spread of MERS-CoV between people in health care facilities. Healthcare workers should always apply standard precautions consistently with all patients, at every interaction in healthcare settings. Droplet precautions should be added to the standard precautions when providing care to patients with symptoms of acute respiratory infection; contact precautions and eye protection should be added when caring for probable or confirmed cases of MERS-CoV infection; airborne precautions should be applied when performing aerosol-generating procedures or in settings where aerosol-generating procedures are conducted. Early identification, case management and isolation of cases, follow-up and quarantine of contacts, together with appropriate IPC measures in health care setting and public health awareness can prevent human-to-human transmission of MERS-CoV.
MERS-CoV appears to cause more severe disease in people with underlying chronic medical conditions such as diabetes, renal failure, chronic lung disease, and immunocompromised persons. Therefore, people with these underlying medical conditions should avoid close contact with animals, particularly dromedaries, when visiting farms, markets, race tracks or slaughterhouses where the virus may be circulating. General hygiene measures, such as regular hand washing before and after touching animals and avoiding contact with sick animals, should be adhered to.
Food hygiene practices should be observed. People should avoid handling or consuming raw camel milk or camel urine or eating meat that has not been properly cooked.
WHO does not advise special screening at points of entry regarding this event, nor does it currently recommend the application of any travel or trade restrictions.
Citable reference: World Health Organization (16 November 2022). Disease Outbreak News; Middle East respiratory syndrome coronavirus (MERS-CoV) – Saudi Arabia. Available at: https://www.who.int/emergencies/disease-outbreak-news/item/2022-DON422