One of the hallmarks of MERS outbreaks in the Middle East and in South Korea has been that the vast majority of large clusters have occurred in health care settings (see WHO Update On Saudi MERS Clusters In Riyadh and Saudi MOH: KKUH Hospital Outbreak As A `Superspreading' Event).
A number of plausible explanations have been offered, including over crowded ER's, performing aerosolizing procedures in a common area, and the rare super-spreading patient who emits higher levels of virus than others.While the MERS outbreaks in the Middle East haven't suggested a `classically airborne' virus like influenza or measles, droplet spread over short distances through the air is assumed and limited airborne transmission seems likely (see mBio: Airborne Fragments Of MERS-CoV Detected In Saudi Camel Barn).
A 2013 study called Stability of Middle East respiratory syndrome coronavirus (MERS-CoV) under different environmental conditions by N van Doremalen1, T Bushmaker1, V J Munster found, under favorable temperature and humidity conditions (such as you might find in an air conditioned hospital), the MERS virus survives quite well both on surfaces, and in the air.
All of which brings us to a new study, published in the Journal of Aerosol Science, which finds the 60-minute survivability of the MERS virus in an air-conditioned environment far exceeds that of the virus under typical Middle Eastern outside environmental conditions.
Journal of Aerosol Science
Survival of aerosolized coronavirus in the ambient air
Oleg V. Pyankova, Sergey A. Bodneva, Olga G. Pyankovaa, Igor E. Agranovskib, ,
• Airborne MERS virus survival has been investigated and characterised.
• The virus demonstrated high survival compared to influenza strains.
• The virus inactivation was found to be more efficient at high air temperature and low humidity.
An inactivation of airborne pathogenic Middle East Respiratory Syndrome (MERS-CoV) virus was investigated under controlled laboratory conditions. Two sets of climatic conditions were used in the experiments; (1) representing common office environment (25 °C and 79% RH) and (2) climatic conditions of the Middle Eastern region where the virus was originated from (38 °C and 24% RH).
At the lower temperature, the virus demonstrated high robustness and strong capability to survive with about 63.5% of microorganisms remaining infectious 60 min after aerosolisation. Fortunately, virus decay was much stronger for hot and dry air scenario with only 4.7% survival over 60 min procedure.(Continue . . .)
If a hot and dry environment provides a major dampening effect on MERS transmission, then that could explain why large community outbreaks (other than household related), haven't been reported. It does raise the question of what happens should the virus be introduced to a region which a more MERS friendly climate.