Why Are Short People Half As Likely to Get Covid-19?

As we've been saying: Downward droplet transmission may be less important than aerosol transmission.

Munchkins are safe.
Munchkins are safe.

 The Wizard of Oz via Getty Images

Randy Newman is proven wrong once again, short people (like me) have every reason to live and to stand tall; a new survey finds that we are twice as resistant to COVID-19 than those over 6 feet tall. That's only one of the findings, but it's the one getting the most attention. The paper draws on data from the US and the UK gathered from 2000 people who had tested positive for COVID-19 in the first week of June 2020. 

  • Not surprisingly, Users of public transit had a higher rate of infection than those who worked from home, though notably, a much higher rate in the US than in the UK.
  • Members of unions had a higher rate of infection. This makes sense, as many of the hospital and transit workers are unionized.
  • Using cash instead of credit cards has a higher risk.
  • Using a shared kitchen is a significant factor.
  • And Surprise! Having a low income significantly increases risk, because of course, poor people have to go to work outside the home, are often overcrowded, and may not have credit or a car.
  • Then there is everybody's favorite: Being a male over six feet increases risk. "The fact that height is a significant predictor for men suggests that downward droplet transmission may be less important than aerosol transmission (particularly prior to lockdown) in which case the use of specifically designed air purifiers should be further explored." More evidence that the virus is transmitted through aerosols and that perhaps tall people have their heads in the virus clouds. 

One of the study authors, Professor Evan Kontopantelis, was surprised by this:

We expected taller men to be more protected when in reality they were not. The findings indicate that aerosol transmission is extremely likely and not only that, taller men have a higher risk in the U.K., possibly because of their behaviour – ‘I am tall and it has crossed my mind that I would be protected if I keep my head high if others sneeze beneath me’ – but it seems these particles go up in the air and linger there for a long time, so everyone needs to protect themselves.

Even though I am short, I am not taking this as a license to hit the bars; the survey was not huge, and only surveyed people who have been tested and diagnosed, who tend to be richer and whiter, and in fact, taller.

And as noted earlier, the evidence of airborne transmission is piling up.

Medical Science Finally Meets Building Science

ventilation do's and don'ts
ventilation do's and don'ts. Lidia Morawska et al

It has taken some time for scientists to agree that the coronavirus can be transmitted through aerosols, but there now appears to be a consensus that, as the New York Times headline says, "Yes, the Coronavirus Is in the Air." The building science community (and Treehugger) have been saying this for a while, and after months of pressure the WHO is finally going, as Dr. Linsey Marr describes it, "from denial to grudging partial acceptance."

Dr. Marr, a civil and environmental engineer, confirms what the engineers said earlier: improve airflow and open windows if you can. Her key recommendations, besides wearing a well-fitting mask:

Avoid crowds. The more people around you, the more likely someone among them will be infected. Especially avoid crowds indoors, where aerosols can accumulate.
Ventilation counts. Open windows and doors. Adjust dampers in air-conditioning and heating systems. Upgrade the filters in those systems. Add portable air cleaners, or install germicidal ultraviolet technologies to remove or kill virus particles in the air.

We have noted before that this is not so easy; many buildings don't have opening windows and those that do probably don't have any cross-ventilation. HVAC systems in North America are designed to recirculate because ventilation and cooling (or heating) are done together so they have to move a lot of air. In hot weather, they don't have the cooling capacity to handle all the fresh air. They may not even be able to have a better filter because it may take a bigger fan to push the air through. 

It's About Time

And yet another study confirms that the coronavirus is airborne, even collecting on return air grilles. Dr. Shelly Miller and other building scientists have been saying this for months. So before the kids are allowed back into school, how about concentrating on building a million portable air filters, installing UVC virus killing lights in ductwork, installing new filters and fans, and cranking up the fresh air, and cleaning those grilles. We've got a month.