Jose-Luis Jimenez: ‘COVID-19 Is Transmitted Through Aerosols. We Need to Adapt.’

Jose-Luis Jimenez, writing in Time:

When it comes to COVID-19, the evidence overwhelmingly supports aerosol transmission, and there are no strong arguments against it. For example, contact tracing has found that much COVID-19 transmission occurs in close proximity, but that many people who share the same home with an infected person do not get the disease. To understand why, it is useful to use cigarette or vaping smoke (which is also an aerosol) as an analog. Imagine sharing a home with a smoker: if you stood close to the smoker while talking, you would inhale a great deal of smoke. Replace the smoke with virus-containing aerosols, which behave very similarly, and the impact is similar: the closer you are to someone releasing virus-carrying aerosols, the more likely you are to breathe in larger amounts of virus. We know from detailed, rigorous studies that when individuals talk in close proximity, aerosols dominate transmission and droplets are nearly negligible.

If you are standing on the other side of the room, you would inhale significantly less smoke. But in a poorly ventilated room, the smoke will accumulate, and people in the room may end up inhaling a lot of smoke over time. Talking, and especially singing and shouting increase aerosol exhalation by factors of 10 and 50, respectively. Indeed, we are finding that outbreaks often occur when people gather in crowded, insufficiently ventilated indoor spaces, such as singing at karaoke parties, cheering at clubs, having conversations in bars, and exercising in gyms. Superspreading events, where one person infects many, occur almost exclusively in indoor locations and are driving the pandemic. These observations are easily explained by aerosols, and are very difficult or impossible to explain by droplets or fomites.

I find this argument incredibly compelling, and the WHO and CDC’s reluctance to embrace it incredibly frustrating. The theory that COVID-19 spreads primarily through aerosols matches everything we know about it.

The upside is that the smoking comparison helps model risk avoidance. Pretend everyone you see is smoking, and try to avoid breathing their exhaled “smoke”. It also goes to show how indoor restaurants and especially bars are just a no-go until COVID-19 is under control. Spacing tables six feet apart wouldn’t keep you from smelling cigarette smoke from fellow patrons at a restaurant, and it won’t keep you from breathing their aerosols.

★ Wednesday, 26 August 2020