September 8, 2020 – Aerosols

In 1990, smoking cigarettes was okay just about everywhere, including in the step-down unit of the coronary care unit at Johns Hopkins Bayview Medical Center where I completed my residency. Patients, fresh from their recent heart attack, could share a cigarette with their CCU nurse. Ah, the good old days.

During this time, I also worked some extra shifts at the Veterans Administration Hospital in Perryville, Maryland. The doctor on call was the only doctor on premises for about 500 patients. The biggest challenge in that job was leaving at 7 am without smelling like smoke.  Every ward, from general medical wards, rehabilitation units, and especially the psychiatric wards, looked like a poker room in a casino – you could barely see through the din of smoke.

Thinking about smoke and the way it travels and lingers may be a good way to envision the behavior of the coronavirus. There is emerging evidence that one of the ways it spreads is in aerosols, for which wafting smoke is a fairly accurate model. Thus far, the prevention of spread of the virus has concentrated on protecting against the transmission of respiratory droplets, which spread ballistically, like when your enthusiastic uncle sprays you with saliva when talking about his golf game at your cousin’s wedding. It is understandable how a mask could keep your uncle’s spittle from hitting your cheek. But your uncle’s aerosols are invisible, drifting through the air and spreading around the room, perhaps descending on you later while you are Bogarting a cream puff at the desert table.

A recent article in Time magazine, ( forwarded to me by a patient, shares a proposal for the prevention of transmission of aerosols summarized by the pneumonic A CIVIC DUTY: Avoid Crowding, Indoors, low Ventilation, Close proximity, long Duration, Unmasked, Talking/singing/Yelling. These practices appear to be common sense, but the fact that the virus is raging on in the United States signals that people are not practicing these measures consistently. Research has shown that being outside may be 20 times safer than being inside in regard to viral transmission. Being inside with a mask that fits snugly is safe and will allow you to go conduct your life as close to normal as possible. Because of the aerosol issue, eating in indoor restaurants, or bars, without a mask (you can’t eat with a mask on) may be the riskiest thing that we do. Even with social distancing inside restaurants, aerosolized virus can travel throughout the room, be taken up by the HVAC system, and be expelled by a vent on the other side of the salad bar where you are inhaling a calzone. There is emerging evidence that this threat may be mitigated by improving HVAC systems with specialized filters and exposing the circulating air to ultraviolet light.

And if I haven’t ruined your day yet, consider this article which appeared last week in the Washington Post entitled: It’s time to talk about how toilets may be spreading covid-19 (link at end of email). The article describes how the act of flushing your commode aerosolizes the contents of fecal matter (including the coronavirus) so that it wafts up above the potty, like a genie ready to grant you a wish. In this case the wish is “don’t let me get that damn virus!” The article, written by a Harvard public health expert, describes how virus contained in a turd in a toilet on the 15^th floor of a Chinese apartment building was detected on the 25^th and 27^th floor of the same building due to a common HVAC system.

Now that I have frightened you from both breathing and relieving yourself, let’s move on to some hard data.  Despite the risks that surround us, Maryland numbers continue to improve, which has led Governor Hogan to liberalize restrictions, opening movie theatres and increasing capacity of restaurants. The percent positivity rate for coronavirus tests in Maryland is under 3.7% for the last week. The number of deaths per day from Covid-19 have remained in the single digits for weeks. Total hospitalizations and ICU admissions in Maryland are at the lowest point since the start of the pandemic. The disease continues to have the most devastating effect on the older populations with just 13.2% of the deaths in Maryland occurring in people under 60 years old.

Nationwide, the virus is taking a road trip from the sunbelt states, which have improved dramatically, to the Midwest, where the viral load in several states is increasing, including in Illinois, Kentucky, the Dakotas, Iowa and Missouri. The daily total case load in the United States is still hovering around 40,000, only slightly less than 2 weeks ago. The total daily deaths in the United States are hovering around 1000 per day, again down only slightly from two weeks ago.

The success of viral containment in Maryland, despite busy streets and businesses is a testament to how we can function safely until a vaccine comes along, hopefully in a few months. Maryland has reported steady and low viral loads for 3 months, evidenced by low hospitalization and death rates, in contrast to many states around the country who can’t seem to follow some pretty simple guidelines. The opening of some school districts and colleges could change the trajectory of the virus here and elsewhere, for the worse. But if these openings are done thoughtfully with monitoring of viral loads, as some colleges have mastered, we should be able to ride this out without a catastrophe.

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