Author: SEOK WOO YANG, MD & PhD (E.mail: soplab@outlook.kr)
Date: 2020.03.04.
Content:
To prevent further spread and contagion of coronavirus 19, two environmental factors like temperature and humidity should be considered.
TEMPERATURE
As one of the key factors facilitating the transmission of Coronaviruses, the environmental temperature has been reported in many articles.
Chan et al(2011) reported that SARS coronavirus could maintain active for at least 5 days on a smooth surface in an environment where the temperature was 22-25℃ and relative humidity 40-50%. This environmental temperature range from 22 to 25℃ is similar to the room temperature, which is 20-22℃. For this reason, these explain why an outbreak of SARS occurred in Hong Kong(subtropical area, the air-conditioned environment in the spring), whereas SARS transmission was not prominent in the tropical areas(such as Malaysia, Indonesia or Thailand) with high temperature and high relative humidity environment.[1]
As a supportive opinion, Ian Lipkin(director of the Columbia University's Center for Infection and Immunity) says sunlight, which is less abundant in winter, can also help break down viruses that have been transmitted to surfaces. The reason for this phenomenon is that UV light with sunlight breaks down nucleic acid. It almost sterilizes surfaces contaminated with coronaviruses. The UV light is so effective at killing bacteria and viruses it’s often used in hospitals to sterilize equipment.[2]
Besides the environmental temperature condition, human nasal and oropharyngeal temperature plays a major role in coronavirus infection.
The optimal temperature for the replication of human coronavirus is 33℃.[3]
During quiet breathing of room air, the average physiologic temperature ranged from 32.0 +/- 0.05 ℃ in the upper trachea to 35.5 +/- 0.3℃ in the subsegmental bronchi.[4]
For this reason, it may explain why human coronavirus infection mainly occurs in the upper respiratory tract(nose, oropharynx, and larynx are included).
HUMIDITY
In a normal healthy state, nose and pharynx secrete and are covered by viscous wet mucus, which is appropriate for trapping virus droplets.
Cold and dry air makes normally viscous wet mucus drier and less efficient for trapping virus particles.
This explains why Coronavirus outbreaks like SARS and COVID 19 happen in the winter season with low environmental temperature and humidity.
SUMMARY
In terms of both environmental and human physiologic upper respiratory tract temperature and humidity, high environmental temperature and humidity can be a key factor to prevent transmission of coronavirus.
As a method to satisfy the above conditions in our body, facial mask, adequate hydration(water intake) and sun exposure can be an alternative.
The facial mask makes human airways keep more humid and warmer, namely high humidity and high temperature, the condition of which inhibits transmission of coronavirus droplets.
REFERENCE
[1] K.H. Chan, J.S.M. Peiris, S.Y. Lam, L.L.M. Poon, K. Yuen, W.H. Seto, The Effects of
Temperature and Relative Humidity on the Viability of the SARS Coronavirus, Advances in
Virology, 2011 (2011) 734690-734690.)
[2] Sarah Gibbens. Will warming spring temperatures slow the coronavirus outbreak?. NATIONAL GEOGRAPHIC. Feb 25. 2020.
[3] M.M. Darville and E.O. Caul. Coronavirus. Chapter 57 In Medical Microbiology Edited by David Greenwood, Richard C.B.Slack, John F.Peutherer. 16th ed. 2002. p548.
[4] McFadden ER Jr, Pichurko BM, Bowman HF, Ingenito E, Burns S, Dowling N,
Solway J. Thermal mapping of the airways in humans. J Appl Physiol (1985). 1985
Feb;58(2):564-70. doi: 10.1152/jappl.1985.58.2.564. PMID: 3980358.
