In the past few weeks, world leaders have had to make very difficult decisions. Lock down entire country? Put money into healthcare? Risk economic disasters to prevent health disaster?
I guess the biggest problem they would have faced in making these decisions is uncertainty. Because medicine is a field of uncertainties. The first thing a doctor learns when helping patients is that they can never be sure of anything other than the fact that they have to act. Diseases, cells, organisms, molecules, environment, human behaviour - there are a lot of moving parts in medicine. Parts that you can't control. Parts that you can't even predict.
A doctor is a performance artist who uses an imperfect science to help alleviate suffering. In Osler's words, "Medicine is a science of uncertainty and an art of probability". I've been fascinated by the range of dilemmas a thinking doctor faces in routine practice. When choosing who gets a ventilator they get to act God. When choosing what information to convey to the spouse of a person newly diagnosed with HIV, they get to play the Supreme Court. And not to forget the countless times they get to act human when seeing raw humanness play out in various scenarios - first breastfeeding of a newborn baby, last bye-byes before surgery (oh, thinking of it, I've never seen a family wave bye-bye in India. Maybe I'm watching too much of medical TV series), pain that persists even with the strongest painkillers, so on.
We were talking about uncertainties. Yes. That's what makes life really difficult in the field of medicine.
Let's take one specific question. The use of masks by public during COVID-19 pandemic. Should they wear it? Should they not?
Let me break it down.
What do we know about how the virus is transmitted? Just enough. We think it is through respiratory droplets and contact.
What does that mean? A respiratory droplet is any drop that comes out of a person's nose or mouth. It could come out while coughing, sneezing, even while laughing, or shouting. Contact is, well, contact. Touch. Touch anywhere where those respiratory droplets could have been. Surfaces, hands, wherever.
Okay. So we know how the virus comes out of a person. But how does it enter someone else? No points for guessing that the respiratory tract is a major route for entry of respiratory viruses into someone. That includes mouth and nose. But turns out respiratory viruses can enter body through eyes too. (Warned you about uncertainties, didn't I?) Luckily for humans, the largest organ of our body - the skin - is also a very protective sheath that makes our hands, legs, and so on less likely to be ports of entry for the virus. (Like I tell the people who come to me scared of HIV because they touched someone infected with HIV, even if a bag of blood full of HIV falls on your bare hands, unless there is a cut on your skin, there is no need to be scared. Of course, they then ask about the possibilities of microscopic cuts. But that's another story and this snippet of that story is included to make a point that there are "risks" and there are risks.)
Now, what do we know about masks? The medical masks that we are talking about? They can definitely protect someone's nose and mouth from other people's respiratory droplets. But that's all they can do. They cannot protect their hands. They cannot protect their eyes. And the mask itself gets contaminated while protecting the mouth and nose of the wearer (Important point. The external surface of the mask is where all those respiratory droplets, if any, should get caught).
What do we know about people? We know that people touch their face a lot. You just touched your face while reading this article. Your nose is itching as you're reading this sentence.
When a human goes out during the pandemic to buy grocery, they have to deal with many things. Around them, there could be a large number of people who have never seen SARS-CoV-2 in their life. They could also be walking among asymptomatic carriers who are shedding their virus in respiratory droplets. They could be touching surfaces which a carrier coughed into 10 minutes before. They could be inhaling respiratory droplets from carriers. Respiratory droplets could land on their eyes. Droplets could land on their hands and they could then touch their eyes/nose inadvertently. Droplets could land on their masks and they could then touch their masks inadvertently. Their mask itself could be a makeshift one with towel that they hold in front of nose and mouth (where the external most surface is their own, pretty, hand). And that hand could then inadvertently touch their eyes/nose.
Do you see the risks and the risks that masks mask (pun intended)?
Yes, theoretically masks decrease the risk of transmission by a tiny bit. But practically, probably, they don't.
On the other hand, there are some real risks of people wearing masks to grocery shops.
The first thing that happens is we all run out of masks. Including the health care workers and people who care for COVID-19 infected at home. (Of course this has already happened in many cities). These people are now at definite risk for contracting infections because they deal with definitely sick people and for very long durations which increases their exposure. Many of the health care workers do not become sick, but some of them do. When they become sick the entire system is demoralized. And we don't want that to happen when we are about to face a pandemic that nobody is sure how to deal with.
That is why WHO and CDC and others insist that masks should be used rationally.
Does that mean, if we had unlimited supply of masks, it would be okay for public to wear it when going out to fetch grocery?
If you are a person who wears a helmet while walking on the road, yes.
Of course, how could I miss this, yesterday when I went to the grocer's, I was wearing a helmet with the glass visor closed all the time.— Akshay S Dinesh (@asdofindia) March 28, 2020
Okay. Update: I haven't considered at all the chance that you're an asymptomatic carrier who is spreading the disease to others. In which case, suddenly there is a non-trivial effect where masks prevent the respiratory droplets from getting out of you in the first place. Uncertainties here are the proportion of asymptomatic carriers and their infectivity.
I really don't know.
Update on May 30: There is piling evidence that masks are useful for source control. And now that the pandemic is well distributed inside all countries, the calculations of risk also has to change. Right now, the governments would have had enough chance to ramp up PPE production and meet healthcare needs. Right now you are at a higher risk of being an asymptomatic carrier than you were at the beginning of the pandemic when overall prevalence was low. So, yes, wear a mask. It may not protect yourself, but it will protect others.
