Category Archives: HEPA filters and Corsi Rosenthal Box

3 Respiratory Viruses Threaten World Health this winter

Winter approaches with a perfect storm of 3 respiratory viruses, increased indoor activity, dry spaces, and holiday gatherings. The 3 viruses already filling many hospitals (including children’s hospitals) include RSV (Respiratory Syncytial Virus), Influenza, and SARS-CoV-2.

Respiratory viruses spread by aerosol typically enter through the nose and throat. Dry nasal and oral-pharyngeal mucosa (the lining of the nose and throat) presents an ideal incubator for respiratory viruses. With winter comes drier indoor environments created by heating systems.

A recently published study concluded:

Indoor conditions, particularly indoor RH (relative humidity) modulate the spread and severity of COVID-19 outbreaks.

The sweet spot was between 40% and 60% humidity to minimize spread and severity of infection.

Here is a picture of the temperature and humidity monitor in my home office.

Note that while outdoor humidity is 55%, indoor humidity is only 34%, short of the “ideal” range for decreased viral transmission and severity. We have a humidifier in our bedroom where the RH is higher.

In addition to a bedroom humidifier we have several HEPA filters dispersed throughout the house. HEPA filters can decrease aerosol (viral load) by 80% or more as can the homemade Corsi-Rosenthal box. HEPA filters and the Corsi-Rosenthal Box also significantly reduce indoor air pollution, potentially protecting us from not only respiratory disease but also heart attacks, strokes, dementia and cancer.

As the winter approaches consider protecting your family and friends from RSV, Influenza, and COVID-19 by utilizing a humidifier and free standing HEPA filters. Improving indoor air quality will have many health benefits.

In the context of the COVID 19 pandemic I will close with the usual summary.

  1. Avoid alcohol consumption (alcohol wreaks havoc with your immunity)
  2. Get plenty of sleep (without adequate sleep your immune system does not work well )
  3. Follow good sleep habits
  4. Exercise, especially out of doors in a green space, supports the immune system
  5. Get some sunshine and make sure you have adequate Vitamin D levels. Supplement with Vitamin D3 to get your levels above 30 ng/ml, >40ng/ml arguably better.
  6. Eat an anti-inflammatory diet rich in micronutrients.
  7. Practice stress reduction like meditation and yoga which improves the immune system
  8. Eliminate sugar-added foods and beverages from your diet. These increase inflammation, cause metabolic dysfunction, and suppress immunity.
  9. Eliminate refined-inflammatory “vegetable oils” from your diet, instead eat healthy fat.
  10. Clean up your home environment and minimize your family’s exposure to environmental toxins by following recommendations at with regards to household products, personal care products, and organic foods. (
  11. Drink water filtered through a high quality system that eliminates most environmental toxins. (Such as a Berkey or reverse osmosis filter)
  12. HEPA filters or the home-made version (Corsi-Rosenthal box) used in your home or workplace can reduce circulating viral load by 80%. This works for any respiratory virus transmitted by aerosol and this winter we have the triple threat of RSV, Influenza, and SARS-CoV-2. It also decreases indoor air pollution.
  13. If you are eligible for vaccination, consider protecting yourself and your neighbor with a few jabs. Age > 50 and/or risk factors (Diabetes, pre-diabetes, insulin resistance, hypertension, obesity, heart disease, COPD, asthma, cancer treatment, immune suppression) suggests benefit from a booster. Risk for complications of boosters in adolescents, especially males, without risk factors, may equal benefit. Previous infection with Covid can be considered as protective as a booster. Discuss risk vs benefits with your doctor.


Eat clean, drink filtered water, love, laugh, exercise outdoors in a greenspace, get some morning sunlight, block the blue light before bed, engage in meaningful work, find a sense of purpose, spend time with those you love, AND sleep well tonight.

Doctor Bob