One of the many unresolved questions that revolves around the ongoing Covid-19 pandemic is whether local outbreaks can depend on ambient conditions like temperature and relative humidity. In this paper, we put forward a model that tries to explain and describe the possible temperature and relative humidity dependence of viral outbreaks controlled by transmission of respiratory droplets . The model has two parts. First, we model the growth rate of the infected population based on a reaction mechanism - the final equations of which are similar to the well-known SIR model. The advantage of modeling the pandemic using the reaction mechanism is that the rate constants have sound physical interpretation and could be modeled using the collision rate theory. As such, the infection rate constant is  shown to be linearly related to the square of the virus laden droplet lifetime. In the second part, we have emulated the respiratory droplets responsible for disease transmission as salt solution droplets and computed their evaporation time accounting for initial droplet cooling, heat and mass transfer and finally crystallization of the salt. The model output favourably compares with the experimentally obtained evaporation characteristics of levitated droplets of pure water and salt solution, respectively, ensuring fidelity of the model. The model shows that the overall evaporation/desiccation time is indeed dependent on ambient temperature and relative humidity . It is shown that the evaporation time of a particular droplet size could also be chosen as the characteristic lifetime of the droplets. Since the droplet evaporation time determines the infection rate constant,  temperature and relative humidity are shown to rather strongly impact the outbreak growth rates.
One of the many unresolved questions that revolves around the Covid-19 pandemic is whether local outbreaks can depend on ambient conditions like temperature and relative humidity. In this paper, we develop a model that tries to explain and describe the temperature and relative humidity sensitivity of respiratory droplets and their possible connection in determining viral outbreaks . The model has two parts. First, we model the growth rate of the infected population based on a reaction mechanism - the final equations of which are similar to the well-known SIR model. The advantage of modeling the pandemic using the reaction mechanism is that the rate constants have sound physical interpretation . The infection rate constant is derived using collision rate theory and shown to be a function of the respiratory droplet lifetime. In the second part, we have emulated the respiratory droplets responsible for disease transmission as salt solution droplets and computed their evaporation time accounting for droplet cooling, heat and mass transfer and finally crystallization of the salt. The model output favourably compares with the experimentally obtained evaporation characteristics of levitated droplets of pure water and salt solution, respectively, ensuring fidelity of the model. Droplet evaporation/desiccation time is indeed dependent on ambient temperature and relative humidity , considered at both outdoor and indoor conditions. Since the droplet evaporation time determines the infection rate constant, ambient temperature and relative humidity are shown to impact the outbreak growth rates.
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ongoing
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put forward
develop
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possible
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dependence of viral outbreaks controlled by transmission of respiratory droplets
sensitivity of respiratory droplets and their possible connection in determining viral outbreaks
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and could be modeled using the collision rate theory. As such, the
. The
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derived using collision rate theory and
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linearly related to the square of the virus laden
a function of the respiratory
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initial
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The model shows that the overall
Droplet
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. It is shown that the evaporation time of a particular droplet size could also be chosen as the characteristic lifetime of the droplets.
, considered at both outdoor and indoor conditions.
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ambient
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rather strongly