Pembroke Park, FL – Viruses such as influenza and the common cold (which is also a type of coronavirus) undergo seasonal changes, with reduced contagiousness in the summer. So with record heat expected in South Florida this week, it begs the question... could hot temperatures slow the virus? The quick answer is it may slow it a bit, but not enough to make a drastic reduction.
According to an article written by Dr. Marc Lipsitch with the Center for Communicable Disease Dynamics, there isn’t much evidence yet to know just how this new virus will be impacted by high temperatures. In his review, he does state that similar coronaviruses (OC43 and HKU1 to be specific) indeed do not spread as well in the summer. But he is quick to point out that it is not yet known if these are truly good indicators of how the novel coronavirus could be impacted. Dr. Lipsitch also points out that the new virus did spread efficiently in Singapore during February, which lies almost directly on the equator. But even this isn’t apples to apples, as factors such as ultraviolet light and day length could also be playing a role.
The review states that environment is just one of four major factors that impact the spread of the virus. Seasonal changes in human immune systems (which tend to be stronger in the summer), increased population immunity over time, and human behavior (such as social distancing) all play a big role.
On the other side, a study from 2011 that studied the impact of temperatures and humidity on another coronavirus, SARS. It showed that higher temperatures and humidity drastically reduced the ability of the virus to spread. The reason is under high humidity especially, the virus is contained in a larger droplet size from a cough or sneeze. These larger droplets settle quickly out of the air. However, if the air is dry, the droplet evaporates quickly, and the virus is much more likely to remain airborne.
But under Safer at Home orders and with many businesses closed, the majority of people will not be outside in the heat anyway. Most will choose to remain indoors in the air conditioning. The SARS virus thrived in temperatures in the 70s, and under drier conditions. The temperature and humidity levels inside would have been ideal for that virus to spread. So outdoor temperatures may only have a limited impact on the contagiousness. Again, human behavior is a major factor.
Dr. Lipsitch sums it up with, “For the novel coronavirus SARS-CoV-2, we have reason to expect that like other betacoronaviruses, it may transmit somewhat more efficiently in winter than summer, though we don’t know the mechanism(s) responsible. The size of the change is expected to be modest, and not enough to stop transmission on its own.”
Social distancing and washing hands will likely remain our greatest tools in the fight against this pandemic.