Why indoor humidity is so important to limiting the spread of the new coronavirus

In this Thursday, March 19, 2020 photo, Sharry and Steve Solomon avoid contact with others by staying at their home, a retirement community in The Villages, Fla. Due to the coronavirus all regularly-scheduled indoor activities were canceled through the end of the month for residents living in what is perhaps the largest concentration of seniors in the U.S. (AP Photo/John Raoux)

When people sneeze or cough, a cloud of spray comes out of their nose or mouth. When the air is dry, the virus in the spray doesn’t swell, so it can travel up to six feet, that’s why people have to stay six feet apart. The exception is if you’re outside and the wind is blowing toward, the spray of the virus would fall short of the six feet. On the other hand, if the wind is blowing from your back and toward the person in front of you, the virus might carry nine or 10 feet. 

As the humidity rises as we get into the warmer weather this spring and perhaps already in southern parts of the country where the humidity tends to be higher this time of year, the virus absorbs some of the humidity from the air and swells and may fall to the ground within two or three feet, so people are not as contagious in more humid conditions.

It is very important to keep yourself hydrated because if you’re hydrated, the membranes in your nose are not dried out. If the membranes are moist, the virus is less likely to penetrate into the membranes and into your body. 

The risk is therefore much greater in your homes and buildings when it’s dry – such as this time of year – as compared to the summertime when the humidity tends to be higher. 

Since air in your house is heated – basically outside air is heated up inside – it’s dried out. And the relative humidity inside a house can be as low as 10 to 20 percent when it’s cold and dry outside. Whereas when it gets warmer and the temperature outside is in the 70s and 80s, the relative humidity in the house may be as high as 50 or 60 percent or even higher.

This can make a big difference in terms of transmission of the virus. Your membranes are more likely to be moist and any coronavirus carried from a sneeze or cough would not travel as far.