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 important. If someone is sick OR infected but not symptomatic with COVID19, the virus can be transmitted by contact with a surface like a doorknob. These surfaces can be cleaned with Clorox type cleaners which are effective against COVID19, flu, and similar viruses.

Frequent handwashing (at least 20 seconds) and keeping your hands away from your face are important.

Important: PUBLIC HEALTH RECOMMENDATIONS FOR INDIVIDUALS OVER AGE 65 AND THOSE WITH CHRONIC DISEASE INCLUDE VACCINATION FOR PNEUMOCCOUS. Contracting pneumococcal pneumonia before or after COVID19 would be very dangerous.

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 WEBSITE PROVIDES INFORMATION FOR EDUCATIONAL PURPOSES ONLY. CONSULT YOUR HEALTH CARE PROVIDER FOR MEDICAL ADVICE.

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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