Influence of Relative Humidity on the Survival of Some Airborne Viruses

Abstract

A system for studying the effects of relative humidity (RH) and temperature on biological aerosols, utilizing a modified toroid for a static aerosol chamber, is described. Studies were conducted at 23 C and at three RH levels (10, 35, and 90%) with four viruses (Newcastle disease virus, infectious bovine rhinotracheitis virus, vesicular stomatitis virus, and Escherichia coli B T3 bacteriophage). Virus loss on aerosol generation was consistently lower at 90% than at 10 or 35% RH. When stored at 23 C, Newcastle disease virus and vesicular stomatitis virus survived best at 10% RH. Infectious bovine rhinotracheitis virus and E. coli B T3 bacteriophage survived storage at 23 C best at 90% RH.

Mechanistic theory predicts the effects of temperature and humidity on inactivation of SARS-CoV-2 and other enveloped viruses

“…Below the ERH, the reaction no longer occurs in solution, and so inactivation may be slower. The non-monotonic (‘U-shaped’) dependence of virus inactivation on relative humidity, observed in our data ( Figure 1a ) and elsewhere in the literature ( Yang et al, 2012 ; Benbough, 1971 ; Prussin et al, 2018 ; Webb et al, 1963 ), including for coronaviruses ( Casanova et al, 2010 ; Songer, 1967 ), could be explained by this regime shift around the ERH ( Figure 1c ).…”

“…Combining novel data, mathematical modeling, and a meta-analysis of existing literature, we have developed a unified, mechanistic framework to quantify the joint effects of temperature and humidity on virus stability. In particular, our model provides a mechanism for the non-linear and non-monotonic relationship between relative humidity and virus stability previously observed for numerous enveloped viruses ( Yang and Marr, 2012 ; Casanova et al, 2010 ; Songer, 1967 ), but not previously reported for SARS-CoV-2. Our work documents and explains the strong dependence of SARS-CoV-2 stability on environmental temperature and relative humidity, and accurately predicts half-lives for five coronavirus species in conditions from 4°C to 95°C, and from 30% to 80% RH and in bulk solution.…”

“…Similar empirical patterns of temperature and humidity dependence to what we measured, and modeled, for SARS-CoV-2 have been observed for other important viruses. In particular, the U-shaped dependence of inactivation on RH has been reported for animal coronaviruses ( Songer, 1967 ; Casanova et al, 2010 ), as well as for influenza viruses, paramyxoviruses, rhabdoviruses, and retroviruses ( Yang et al, 2012 ; Benbough, 1971 ; Prussin et al, 2018 ; Webb et al, 1963 ), suggesting the existence of a shared mechanism for the effect of humidity across enveloped RNA viruses. Some enveloped DNA viruses such as herpesviruses and poxviruses ( Songer, 1967 ; Webb et al, 1963 ) and some encapsulated viruses such as polioviruses ( de Jong and Winkler, 1968 ; Songer, 1967 ) also show similar empirical behavior.…”

“…In particular, the U-shaped dependence of inactivation on RH has been reported for animal coronaviruses ( Songer, 1967 ; Casanova et al, 2010 ), as well as for influenza viruses, paramyxoviruses, rhabdoviruses, and retroviruses ( Yang et al, 2012 ; Benbough, 1971 ; Prussin et al, 2018 ; Webb et al, 1963 ), suggesting the existence of a shared mechanism for the effect of humidity across enveloped RNA viruses. Some enveloped DNA viruses such as herpesviruses and poxviruses ( Songer, 1967 ; Webb et al, 1963 ) and some encapsulated viruses such as polioviruses ( de Jong and Winkler, 1968 ; Songer, 1967 ) also show similar empirical behavior. Experiments have found that heat treatment of viruses reduces infectivity principally by degrading surface proteins ( Wigginton et al, 2012 ), lending further support to a chemical model of environmental virus inactivation.…”

Airborne transmission of respiratory viruses

“…Animal studies have shown that influenza virus transmission is favored at low RH ( 135 , 137 ); however, a study of the 2009 pandemic influenza A virus (H1N1) in more physiologically realistic medium reported that the virus remained highly stable and infectious over a broad RH range between 20 and 100% ( 138 ). A study investigated the sensitivity of 11 airborne viruses to RH and found that although some RNA viruses survived best at low RH, other viruses survived better at high RH ( 139 ). The relationship between RH and virus viability in droplets and aerosols is characteristic to the virus, modulated by both the intrinsic physicochemical properties of the virus and its surrounding environment ( 113 , 129 , 139 ) ( Fig.…”