– Top Ebola Scientists: Ebola More Likely to be Spread by Aerosol In Cold, Dry Conditions than In Hot, Humid Africa (Washington’s Blog, Oct 25, 2014):
Army’s Infectious Disease Research Unit and Discoverer of Ebola Strain Agree
We’ve repeatedly warned that this strain of Ebola might be spread by aerosols.
But there is a fascinating and terrifying wrinkle to this …
You might assume that hot, steamy places would be more likely to spread deadly germs than developed countries. But the opposite might be true.
In 1995, scientists from the US Army Medical Research Institute of Infectious Diseases (USAMRIID) reported in the International Journal of Experimental Pathology:
We also demonstrated aerosol transmission of Ebola virus at lower temperature and humidity than that normally present in sub-Saharan Africa. Ebola virus sensitivity to the high temperatures and humidity in the thatched, mud, and wattel huts shared by infected family members in southern Sudan and northern Zaire may have been a factor limiting aerosol transmission of Ebola virus in the African epidemics. Both elevated temperature and relative humidity (RH) have been shown to reduce the aerosol stability of viruses (Songer 1967). Our experiments were conducted at 240C [i.e. 75 degrees Fahrenheit] and < 40% RH, conditions which are known to favour the aerosol stability of at least two other African haemorrhagic fever viruses, Rift Valley fever and Lassa (Stephenson et a/. 1984; Anderson et a/. 1991). If the same holds true for filoviruses [Ebola is a type of filovirus], aerosol transmission is a greater threat in modern hospital or laboratory settings than it is in the natural climatic ranges of viruses.
Peter Jahrling was one of the authors of the report. Jahrling was discoverer of the Reston strain of Ebola, and is now chief scientist at the U.S. National Institute of Allergy and Infectious Diseases.
In 2012, scientists from USAMRIID published a report in the journal Viruses finding:
Aerosol transmission is thought to be possible and may occur in conditions of lower temperature and humidity which may not have been factors in outbreaks in warmer climates.
Given that this is the first time that Ebola has spread out of West Africa to cooler, dryer nations, we may soon find out whether or not high temperature and humidity really do suppress the spread of Ebola by aerosols.