Fall conjures visions of stunning foliage and pumpkin flavored treats, but it also brings along some less welcome visitors: an annual resurgence in cases of the flu, the common cold, and other respiratory viruses. This year, however, the first chill in the air feels particularly concerning as the cold and flu season in the Northern Hemisphere overlaps with the Covid-19 pandemic.
Why might the addition of Covid-19 to our typical cold and flu season create a double whammy? First, there is the concern of a strain on our healthcare system if there is an influx of flu patients on top of Covid-19 patients. The flu is itself a serious illness: in the last flu season in the U.S. alone, there were 39-56 million flu cases, 18-26 million medical visits, 410,000-740,000 hospitalizations, and 24,000-62,000 deaths. We also don’t yet know how the flu and Covid-19 might interact if someone is infected at the same time, and whether it might increase the risk of severe illness or transmission. To top it all off, the different illnesses circulating simultaneously may simply create worry and stress for people at a time when levels are already high. The anxiety of wondering if one’s symptoms are from Covid-19 or the common cold, or if your sniffles are a sign to make arrangements for quarantine, are the last thing many people need right now. Many healthcare systems offer online guidance about how to distinguish symptoms of the different illnesses, such as this discussion from Cleveland Clinic.
This year, cases of the flu appeared to be much lower than normal in the Southern Hemisphere, which experiences fall and winter earlier than the Northern Hemisphere and is usually indicative of what the North should expect during their cold season. Experts believe that the decline may be due to restrictions that were put in place to prevent the spread of Covid-19, which simultaneously prevented the spread of other viruses. Alternatively, it may be due to people staying home when they would otherwise have sought medical care. So while Southern trends may indicate a milder flu and cold season in the North, health officials warn against complacency and urge people to maintain precautions, especially in the context of Covid-19.
Flus and colds tend to strike more aggressively in cooler weather, for several reasons. People spend more time indoors in close proximity to one another, which creates more favorable conditions for viruses to spread from person to person. The influenza virus also appears to survive longer in colder, less humid weather. Finally, cold temperatures may negatively impact the body’s immune system response, which can make it more difficult to fight off infections. These factors may also apply to the virus causing Covid-19.
This article is the first one in a two-part series, where we share some key indoor environment-based precautions to help mitigate and manage your risk of catching the cold, flu, and/or Covid-19. Stay tuned for the second one where we explore hygiene, vaccine and immune health-based strategies to help manage your risk of cold and flu this season.
Make Your Environment Work for You
The many personal hygiene and behavioral precautions we now take to reduce our risk of Covid-19, as well as strategies we employ to strengthen our immune systems, all work well together to reduce our odds of getting sick with the cold and/or flu. However, it is also critical that we leverage indoor environmental factors to create healthier spaces that can help reduce our risk of getting sick.
Ensure Adequate Ventilation Indoors
We have long understood that lack of ventilation increases our risk of respiratory illnesses, and that ventilating indoor spaces promotes the circulation of fresh air that is low in, or free from, particles that carry harmful bacteria or viruses. If there are viral particles present in the indoor air, increasing ventilation by introducing outdoor fresh air can dilute the viral load within the air indoors, and thus reduce your chances of being exposed to the virus.
To help maintain adequate ventilation in your environment, open the windows as frequently as possible (if you rely on natural ventilation), or set your mechanical ventilation to 100% (or as high as possible) fresh air intake. In addition, disable demand-control ventilation controls that reduce air supply based on temperature and occupancy, and set your mechanical ventilation to 100% (or as high as possible) fresh air intake mode. If you rely on natural ventilation, you can also place a regular box fan by the window to help pull in fresh air.
When you open your windows, remember to check the outdoor air quality to make sure that pollutant and pollen levels in your area are low. You can check outdoor air quality in your area using an air quality reporting service.
Purify Your Indoor Air
Air purification systems are considered to be a critical supplementary approach to reducing transmission rates of airborne diseases, including Covid-19, as they help remediate airborne pollutants and contaminants in indoor spaces. To reduce the airborne viral load in your home, you can use either in-duct or stand-alone air purification systems; both types of systems may be able capture and remove aerosolized particles that may contain SARS-CoV-2, the virus that causes Covid-19. While some airborne viruses may aggregate to form larger particles (usually bigger than 0.16 microns), opt for an air filtration technology that effectively captures and removes ultrafine or aerosolized particles (smaller than 0.1 micrometers), to better target viruses in the air.
Humidify Indoor Spaces
Heating our indoor spaces during the fall and winter months helps to maintain a thermally comfortable environment. However, it also dries out the air, often resulting in lower than optimal humidity levels. We know that low humidity has been associated with the onset of the flu season, as well as with increased odds of survival and transmissibility of the flu virus. Therefore, humidifying spaces during the heating season may help to mitigate viral transmission. Experts recommend maintaining indoor humidity levels between 40% and 60% in order to help limit the survival and spread of SARS-CoV-2. To achieve this, you can use standalone (portable) humidifiers and monitor the humidity levels in your space. There are many humidifiers available to purchase online, as well as inexpensive relative humidity monitors. To learn more about the health impacts of humidity levels in your indoor environment, check out our recent article: Can Indoor Humidity Impact Covid-19 Transmission?
Ensure Adequate Temperature
The drop in temperature that occurs as we transition from summer to fall and winter has been shown to diminish our immune system response, which is one of the reasons we are more prone to respiratory infections during the colder months. In addition, declining temperatures combined with decreasing humidity (but not low temperature and humidity per se) have been shown to result in more influenza infections in colder climates. Therefore, ensuring adequate indoor heating during the colder months and maintaining a comfortable temperature may offer protection against seasonal illnesses. Preliminary research in Japan has shown that children who lived in homes with heated bedrooms had fewer respiratory infections compared to those sleeping in unheated environments.
Clean and Disinfect High Touch Surfaces Regularly
Germs and viruses can be found on many high-touch surfaces, which can then help spread infectious illnesses including the common cold and flu. Make sure to clean (wipe down visible dirt) and disinfect (inactivate pathogens such as bacteria and viruses) frequently touched surfaces such as tables, doorknobs, phones, and faucets. The EPA has developed a list of common household disinfectants shown to be effective against the Covid-19 virus, which you can also use to combat cold and flu viruses.
Edited by Bing Bing Guo, MPH and Radhika Singh