MERS-CoV: biological principles for the control of MERS-CoV
This guidance outlines the current knowledge and assumptions about the biology and transmission of Middle East respiratory syndrome coronavirus (MERS-CoV).
Applies to England
Purpose
This document outlines the current knowledge and assumptions about the biology and transmission of MERS-CoV to be used to develop an evidence-based response to cases of infection.
Audience
The biological principles will be of use to public health professionals, NHS and other health and social care staff as well as other organisations and settings developing operational MERS-CoV guidance.
Assumptions about transmission and biology of MERS-CoV
MERS-CoV is a zoonotic respiratory virus and the causative agent of Middle East respiratory syndrome (MERS). MERS-CoV is a coronavirus, first identified in the Kingdom of Saudi Arabia (KSA) in 2012. Analysis of virus genomes suggests that it may have originated in bats and subsequently transmitted to camels. The following assumptions are based on the available data and expert opinions. These assumptions will be regularly reviewed against emerging evidence and updated where appropriate.
Clinical features, incubation, and infectious periods
The incubation period for MERS-CoV is up to 14 days. The infectious period is unknown. Whilst respiratory secretions from MERS-CoV patients have been shown to contain viable virus up to 4 weeks from symptom onset, transmission has only been documented from symptomatic cases.
MERS-CoV can cause a range of clinical features in humans, from mild to fatal. Typical symptoms include fever, cough, and shortness of breath, which can progress to severe pneumonia, acute respiratory distress syndrome (ARDS), and multi-organ failure. Gastrointestinal symptoms such as diarrhoea and vomiting have also been reported.
Whilst infections can be asymptomatic or mild, the case fatality rate (CFR) of MERS-CoV cases reported to the World Health Organization (WHO) is 36%.
Severe and fatal disease has been shown to occur more commonly in cases with zoonotic infection than in those which resulted from human-to-human transmission. This is likely due to active case finding identifying cases with milder disease.
Most cases of MERS-CoV infection in children without any underlying conditions have been asymptomatic and were identified during contact investigations of older patients.
Transmission
The host species for MERS-CoV is thought to be the dromedary camel, and animal-to-human transmission of the virus can occur when people are in contact with infected camels or products such as camel milk or meat. MERS-CoV has been identified in dromedary camels in the Middle East, Africa, and South Asia, but approximately 84% of human cases have been reported by the Kingdom of Saudi Arabia (KSA).
There are 2 clades of MERS-CoV circulating currently; clade B and C. Clade C viruses circulate in Africa. There have been no PCR-confirmed human infections with clade C MERS-CoV to date, although there is serological evidence of prior infection in people occupationally exposed to camels.
Clade B MERS-CoV circulates in the Middle East, further characterised into several sub clades, B1 to B5. Clade B5 is currently enzootic in camels in the Middle East, Kingdom of Saudi Arabia in particular, and the most recent human cases have been characterised as clade B5 viruses. Recent clade B5 sequences from camels have S459N, H486Y, L495P R505L, and V527L mutations in the receptor binding domain (RBD) of the spike protein. The mutations L495P and V527L 21 are exposed to the spike surface and are major targets for human neutralizing antibodies. Studies are ongoing to identify whether those mutations are immune evasive in camels.
There are several B5 subclades in camels in the Kingdom of Saudi Arabia (B5.2023.1 to B.5 2023.5). There are numerous mutations in these subclades identified in virus sequences from camel infections, but they have not been identified in humans to date.
Preliminary sequence analysis from the 2 most recent human cases, detected in November 2025 in France, shows the spike aligns closely with B5 2023.1 and B5 2023.2 subclades. There is a suggestion that this may be a recombinant virus.
MERS-CoV has been found to be detected with a higher viral load and longer duration in the lower respiratory tract than the upper respiratory tract. The virus has also been detected in faeces, serum, urine, and blood samples.
There is limited data on the duration of viral shedding, but patients with MERS-CoV pneumonia have been found to have detectable viral RNA in faeces, rectal swabs, serum and whole blood for 2 weeks, and viable virus (sub genomic mRNA and culturable virus) in respiratory secretions for up to 4 weeks.
Human-to-human transmission has been documented in individuals with close household contact with cases, and in healthcare workers managing cases. Nosocomial outbreaks have been reported from KSA, the United Arab Emirates (UAE) and the Republic of Korea, including in haemodialysis and intensive care units. Systematic and strict implementation of infection prevention and control measures in reported clusters in healthcare settings has appeared to limit onward transmission to healthcare workers and hospitalised patients.
The presence of symptoms appears associated with increased risk of transmission. Evidence suggests that transmission from mild cases is limited, and there is currently a lack of evidence to understand transmission from asymptomatic cases. There has been no evidence of sustained community human-to-human transmission.
Clinically at-risk groups
Studies suggest that older patients, patients with underlying conditions (including diabetes, hypertension, chronic cardiac and renal disease) and patients who are immunosuppressed are at higher risk of severe and fatal disease from MERS-CoV.
Virus survival
MERS-CoV remains viable at 48 hours at 20°C and 40% relative humidity, which is comparable to an indoor environment on plastic and metal surfaces.
MERS-CoV virions are sensitive to heat, lipid solvents, non-ionic detergents, oxidising agents and ultraviolet light.
In aerosol experiments, MERS-CoV retains most of its viability at 20°C and 40% relative humidity. However, viability decreases at higher temperatures or higher levels of relative humidity.
In unpasteurised camel milk, MERS-CoV remains viable beyond 72 hours after introduction, but infectious viruses have not been found after pasteurisation.
MERS-CoV is less stable than SARS-CoV-2 in the environment and is susceptible to sodium hypochlorite 1,000 ppm with a contact time of one minute.
Implications
MERS-CoV is classed as a high consequence infectious disease (HCID) and therefore requires management through HCID pathways in healthcare settings utilising agreed HCID protocols to ensure staff safety. Patients who are under investigation or confirmed to have MERS-CoV infection should be isolated in an airborne infection isolation room and be placed on strict contact, droplet, and airborne precautions.
Personal protective equipment (PPE)
MERS-CoV is classed as a HCID. Information on safe systems of working and PPE requirements for suspected and confirmed HCIDs can be found in the NIPCM and the Addendum on HCID PPE.
Cleaning and decontamination
Linen and laundry from suspected and confirmed cases should be managed as infectious linen and laundry in accordance with Health Technical Memorandum 01-04: Decontamination of linen for health and social care. Waste generated in the care of patients with MERS-CoV infection, including laboratory waste and used PPE, is considered Category B waste, and should be handled in accordance with HTM 07-01 Safe and sustainable management of healthcare waste.
Rooms occupied by suspected or confirmed cases of MERS-CoV should be terminally cleaned followed using a bleach-based disinfectant. MERS-CoV can be inactivated by sodium hypochlorite 1,000 ppm with a contact time of one minute.