Droplets vs Aerosol spread, COVID19

I spoke to a friend who was the Public Health Officer for Sacramento County for many years. She still consults on infectious disease and public health.

There is an important distinction between DROPLET spread and AEROSOL spread.

TB and measles are examples of AEROSOL spread. If someone coughs or sneezes in a room the particles can remain suspended in the air for long periods of time. So if you walk into the room after someone coughs or sneezes you can get the disease. This transmission requires “negative pressure” rooms in a hospital for isolation.

Corona virus and flu were believed to be different. They were thought to be spread by droplets which do not remain suspended in the air. The infected person must sneeze or cough droplets in your face or you must get the droplets from a contaminated surface (example: door knob) and then touch your face. In hospitals this requires only closing the door of the hospital room, not a negative pressure room (the negative pressure does not allow the aerosol to leave the room and it filters the room air).

Since this original post more scientific data have become available that strongly suggest that aerosol spread can occur with SARS CO2, (COVID-19) in community circumstances. Likelihood of transmission increases depending on many variables:

  • enclosed space (meeting room, bar, restaurant, living room, etc.)
  • poor ventilation (windows not open, air turnover from HVAC slow)
  • duration of exposure (time spent in enclosed area, or outside face to face contact)
  • proximity of individuals to one another (need to wear effective masks and socially distance)
  • proximity to air flow from HVAC system which can circulate aerosol
  • viral load of infected individual
  • immune status of individual
  • yelling, loud talking, singing, coughing, sneezing, dramatically increase aerosol and droplet production and transmission distance

Masks and social distancing decrease spread.

Some never develop symptoms. Asymptomatic individuals can carry and transmit the virus.

In individuals who develop symptoms, transmission can occur several days before symptoms appear.

Surfaces like doorknobs, keyboards, tables are not as important as previously thought. If someone is sick OR infected but not symptomatic with COVID19, the virus was thought previously to be transmitted by contact with a surface like a doorknob. cleaning these surfaces with Clorox or similar virus killing antiseptics was considered essential. Now we know that transmission by that route is much less important. AEOROSOL TRANSMISSION is the primary mode of transmission.

Nevertheless, frequent handwashing (at least 20 seconds) would be prudent.


It is unlikely that there will be an effective COVID19 vaccine for a long time, if ever. Why? Because corona viruses MUTATE QUICKLY. There has never been an effective corona virus vaccine. But huge resources are now devoted to developing a vaccine and new technologies and approaches are being tried. (This was posted March 12, 2020, 9 months later a vaccine was available. However the “MUTATE QUICKLY” concern has proven true. As of 11/12/2022 we are still dealing with rapidly developing mutations with increasing immune evasion characteristics. But we have PAXLOVID, a combination anti-viral that is very effective in reducing morbidity, mortality, and risk of LONG COVID.

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 EWG.org with regards to household products, personal care products, and organic foods. (https://www.ewg.org/)
  11. Drink water filtered through a high quality system that eliminates most environmental toxins.
  12. HEPA filters or the home-made version (Corsi-Rosenthal box) used in your home or workplace can reduce circulating viral load as discussed on this website.
  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

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