The flu season coincides with people spending more time indoors. There are several reasons why this is so.
Heated indoor air dries up any droplets emitted while talking, coughing, sneezing, singing, or shouting. (People like to cheer for their teams while watching them on TV).
Once the respiratory droplets are dry, the remaining viruses tend to get suspended in the air longer. The salts from the droplets also crystalize to form a protective covering around the virus.
The low humidity lowers the immune system of the host. The respiratory epithelium or inner lining of the nose and throat has hairy cells called cilia. Cilia needs to move freely to sweep away inhaled viruses. Dry air also disables the cilia and makes the mucus thick making it hard to dispose of germs.
With those factors in mind, scientists from The European Organization for Nuclear Research, also known as CERN, investigated how to decrease airborne transmission of SARS-CoV-2. Their study is published as Modelling airborne transmission of SARS-CoV-2 using CARA: Risk assessment for enclosed spaces as a preprint in medrxiv.
Their investigation found that 20% of infected people, the super emitters, can emit virus particles 100 times more than uninfected.
We found that 20% of infected hosts can emit approximately 2 orders of magnitude more viral-containing particles, suggesting the importance of super-emitters in airborne transmission.
They found that if the super emitter wears a surgical mask, there is a 5-fold reduction in viral emission.
Another way to decrease viral load indoors is to keep the windows open. Open windows provide circulating air that dramatically reduces viruses floating in the air. Slightly opening a window during wintertime ( 20 cm opening) causes a 14-fold reduction in suspended viruses.
Keeping the windows partially open all the time is better than opening them intermittently.
If open windows are too cold, too distracting, or if the air is polluted, they recommend HEPA filters. The use of air cleaners with HEPA filters during winter are comparable to opening the windows during summer.
Considering that vaccination effectiveness wanes after six to eight months and the increased transmissibility of the Delta variant, the authors further said that slightly opening the windows is more effective than vaccination.
Vaccination and host immunity is an important preventive and protective measure, however, according to this model, non-pharmaceutical interventions such as ventilation, seem to be much more effective with a 14 fold reduction.
Take Away Message
Today, the article is relevant to the combination of the COVID-19 pandemic, the lower temperatures, and the start of the flu season. Enclosed space increases the viral load and hence the transmission of influenza and SARS-CoV-2 virus.
Add to that the waning effectiveness of the vaccines and the emergence of variants. And the most vulnerable, like the elderly and the very young, are the ones who stay indoors the longest. Many can potentially get sick.
The study shows the efficacy of mask-wearing among infected people. The problem with that is some carriers may be asymptomatic. Or they may think that their symptoms are from some other condition. Headaches may be from sinus congestion. An allergy may explain a stuffy nose. How many times have you heard, “I have a smoker’s cough”?
Wear a mask indoors if there are any symptoms like cough, itchy throat, stuffy nose, loss of smell or taste, and headaches. Vaccinated people are known to carry 251 times more SARS-CoV-2. In that study, most of the infected were asymptomatic.
Heating cost is projected to increase by 54% this winter. An alternative to opening windows would be this Levoit Air Purifier with True HEPA filters. It is on a limited-time deal on Amazon. I bought two.
This winter season may be one for the books if antibody-dependent enhancement or ADE will increases. We already see signs of ADE in a recent report from the UK.
Simple measures to lower the indoor viral load with mask-wearing, ventilation, and HEPA filters may prevent a lot of future grief and expense.
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Don’t Get Sick!
Related:
- Highest Viral Loads among Delta Variant compared to other Variants: French Study
- Can Breathing Spread the Spike Protein?
- Can Breathing spread the Spike Protein?
- Who, Where, and What can get you infected with COVID-19?
- How Far Can a Sneeze Go?
- Covid-19 Spread with Air-conditioning
- Who, Where, and What can get you infected with COVID-19?
- A Sustainable Way to Decontaminate a Face Mask Using Household Materials
- Obesity is a Risk Factor for Covid-19 Hospitalization
- Yale University’s Take on Cloth Masks for Everyone
- SARS-CoV-2 Contamination in the Hospital Setting
- How Long Can the Covid-19 Virus Survive in Common Surfaces?
Reference:
Image credit: Blausen.com staff (2014). " Medical gallery of Blausen Medical 2014". WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.010. ISSN 2002-4436. – Own work, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=28761835
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