A team of researchers at the University of Maryland School of Medicine's Institute of Human Virology (IHV), which is part of the Global Virus Network (GVN), predicts that COVID-19 is likely follow a seasonal pattern similar to other respiratory viruses like seasonal flu. Their findings are based on on weather modeling data in countries where the virus has taken hold and spread within the community.
In a paper titled “ Temperature and Latitude Analysis to Predict Potential Spread and Seasonality for COVID-19” , the researchers found that all cities that have experienced significant outbreaks of COVID-19 have :
- Similar winter climates with an average temperature of 41 to 52 degrees Fahrenheit (5 to 11.11 degree celsius)
- An average humidity level of 47 to 79 percent with a narrow east-west distribution along the same 30-50 N latitude.
Wuhan in China, South Korea, Japan, Iran, Northern Italy, Seattle, and Northern California have similar weather and humidity patterns.
“Based on what we have documented so far, it appears that the virus has a harder time spreading between people in warmer, tropical climates,” said study leader Mohammad Sajadi, MD, associate professor of medicine, UMSOM, physician-scientist at IHV, and a member of GVN.
The team based its predictions on weather data from the previous few months as well as typical patterns from last year to hypothesize on community spread within the next few weeks. “Using 2019 temperature data for March and April, risk of community spread could be predicted to occur in areas just north of the current areas at risk,” said study co-author Augustin Vintzileos, PhD, assistant research scientist in the Earth System Science Interdisciplinary Center at the University of Maryland, College Park. They plan to investigate whether weather and climate forecasts could help provide more certainty to the predictions.
In areas where the virus has already spread within the community, like Wuhan, Milan, and Tokyo, temperatures did not dip below the freezing mark, the researchers pointed out. They also based their predictions on a study of the novel coronavirus in the laboratory, which found that a temperature of 39 degrees Fahrenheit and humidity level of 20 to 80 percent is most conducive to the virus’ survival.
“Through this extensive research, it has been determined that weather modeling could potentially explain the spread of COVID-19, making it possible to predict the regions that are most likely to be at higher risk of significant community spread in the near future,” said Robert C. Gallo, MD, co-founder and director, IHV, and co-founder and chairman of the International Scientific Leadership Board of GVN. Gallo is also the Homer & Martha Gudelsky Distinguished Professor at UMSOM. “In addition to climate variables, there are multiple factors to be considered when dealing with a pandemic, such as human population densities, human factors, viral genetic evolution, and pathogenesis. This work illustrates how collaborative research can contribute to understanding, mitigating, and preventing infectious threats.”
Gallo is a co-founder of GVN, which is a consortium of leading virologists spanning 53 Centers of Excellence and nine affiliates in 32 countries worldwide, working collaboratively to train the next generation, advance knowledge about how to identify and diagnose pandemic viruses, mitigate and control how such viruses spread and make us sick, as well as develop drugs, vaccines, and treatments to combat them. The network has been meeting regularly to discuss the COVID-19 pandemic, sharing their expertise in all viral areas and their research findings.
According to the paper “Temperature and humidity are also known factors in SARS-CoV, MERS-CoV and influenza survival. Furthermore, new outbreaks occurred during periods of prolonged time at these temperatures, perhaps pointing to increased risk of outbreaks with prolonged conditions in this range. Besides potentially prolonging half-life and viability of the virus, other potential mechanisms associated with cold temperature and low humidity include stabilization of the droplet and enhanced propagation in nasal mucosa, as has been demonstrated with other respiratory viruses.”
It also added that " Even colder areas in the more Northern latitudes have been relatively free of COVID-19 pointing to a potential minimum range for the temperature, which could be due to avoidance of freeze-thaw cycles that could affect virus viability or other factors (at least one human coronaviruses tested is freeze-thaw resistant). All of the above points to a potential direct relation between temperature and SARS-CoV2 environmental survival and spreading. This hypothesis can be tested in experimental conditions similar to work that has been done before, environmental sample testing from areas of ongoing infection, and close epidemiologic and climate studies in the coming weeks.