Low ambient humidity impairs barrier function and innate resistance against influenza infection

Abstract

In the temperate regions, seasonal influenza virus outbreaks correlate closely with decreases in humidity. While low ambient humidity is known to enhance viral transmission, its impact on host response to influenza virus infection and disease outcome remains unclear. Here, we showed that housing Mx1 congenic mice in low relative humidity makes mice more susceptible to severe disease following respiratory challenge with influenza A virus. We find that inhalation of dry air impairs mucociliary clearance, innate antiviral defense, and tissue repair. Moreover, disease exacerbated by low relative humidity was ameliorated in caspase-1/11–deficient Mx1 mice, independent of viral burden. Single-cell RNA sequencing revealed that induction of IFN-stimulated genes in response to viral infection was diminished in multiple cell types in the lung of mice housed in low humidity condition. These results indicate that exposure to dry air impairs host defense against influenza infection, reduces tissue repair, and inflicts caspase-dependent disease pathology.

2019 Novel Coronavirus (COVID-19) Pandemic: Built Environment Considerations To Reduce Transmission

“…Higher humidity likely negatively impacts lipid-enveloped viruses, like CoVs, through interactions with the polar membrane heads that lead to conformational changes of the membrane, causing disruption and inactivation of the virus (70,71). Furthermore, changes in humidity can impact how susceptible an individual is to infection by viral particles (72) and how far into the respiratory tract viral particles are likely to deposit (68). Decreased RH has been demonstrated to decrease mucociliary clearance of invading pathogens and weakened innate immune response (72)(73)(74).…”

“…Furthermore, changes in humidity can impact how susceptible an individual is to infection by viral particles (72) and how far into the respiratory tract viral particles are likely to deposit (68). Decreased RH has been demonstrated to decrease mucociliary clearance of invading pathogens and weakened innate immune response (72)(73)(74). However, RH above 80% may begin to promote mold growth, inducing potentially detrimental health effects (75).…”

Potential Factors Influencing Repeated SARS Outbreaks in China

“…In addition, human cells release signal proteins after viral infection to alert neighboring cells to consider the danger of virus invasion. However, in low-humidity environments, this innate immune defense system is impaired [18]. More seriously, low humidity can cause nasal mucus to become dry; nasal cavity lining to become fragile, or even ruptured; and make the entire upper respiratory tract vulnerable to virus invasion [19].…”

Effects of temperature and humidity on the spread of COVID-19: A systematic review

“…[11,38] The main reasons are: the virus is more stable in cold temperatures, and respiratory droplets, as containers of viruses, remain in suspension longer in dry air [44]. Cold and dry weather can also demote the hosts' immunity and make them more susceptible to the virus [45]. Many respiratory pathogens show seasonality and the human activity patterns and immunity can be influenced by environmental factors limited during the COVID-19 outbreak, due to the absence of extreme climatic conditions and specific immunity for a newly emerging virus [35].…”