Tuesday, September 8, 2020

COVID-19 and Photography: Part 1a, Update - Understanding how the virus spreads

COVID-19 Virus (Image Courtesy of the CDC)In the U.S., COVID-19 has already killed more than 193,000 people. It's done it in less than seven months. COVID-19 is a serious, highly infectious coronavirus. Since writing Part 1 of this series, nothing has changed about how serious the virus is and that photographers, amateurs and professionals alike, need to determine how to safely make photographs in the COVID-19 pandemic world. The photographic community needs to not only remain stay safe and healthy, but ensure, to the extent possible, that we don't spread the disease to others while making photographs.

While much about COVID-19 is still unknown, since writing Part 1 in late June, scientists have learned a great deal more about how the virus spreads. Here's what we know at this time.

COVID-19 transmission is primarily person-to-person.

The Centers for Disease Control and Prevention (CDC) has said for months that the primary way that COVID-19 spreads is person-to-person. Scientist are now questioning what the primary person to person transmission method of the virus actually is.

Up until recently it was thought that COVID-19 is spread mainly between people who are near to each other, six feet or closer, via respiratory droplets expelled from an infected person when they cough, sneeze, or merely talk. The droplets are inhaled by those nearby, infecting them. As a result, the CDC has been recommending that everyone “socially distance” by staying six feet or further from those around us. The CDC has also recommended that everyone wear face masks, particularly when closer than six feet from each other.

Evidence is quickly emerging that the primary method of person-to person transmission of COVID-19 is through airborne aerosols.

In a major paper published by the American Association for the Advancement of Science, the authors argue that the primary method of COVID-19 transmission is through airborne aerosols. In addition, 239 scientists are supporting the two authors of an open letter agreeing with the paper in Science that aerosol transmission is definitely a major transmission method for COVID-19 and likely is the major transmission method.

The scientists explain that as the COVID-19 virus is only 0.1 microns in diameter there is plenty of room for the virus to stay in the air in aerosols that run 50 microns and smaller. When we look at the data from COVID-19 contact tracing, we see that transmission occurs in people in close proximity to each other, but that many times people in the household with an infected person don't get the disease. We also see from the data that the superspreading events where one person has inspected many others have occurred almost exclusively inside, where we can deduce that the ventilation was such that the quantity of virus built up in the indoor area. Finally we know from rigorous studies performed in the past that when individuals talk in close proximity aerosols dominate respiratory transmission and droplets are essentially negligible.

Two other aspects about person-to-person transmission of the virus are particularly important. First, according to public health experts, the COVID-19 virus can be spread by people who are infected, whether or not they're symptomatic. Second, you can be further than six feet from an infected person and still become infected from them, but as you get further away, the likelihood of infection decreases.

Deviations from the “6 foot rule” to social distance further point to aerosol transmission.

In addition, scientists have now uncovered important deviations from their proximity assumptions. For example, during exercise people expel more air, more forcefully, than people standing, sitting or walking at a leisurely pace. As a result, the respiratory droplets in their breath will be driven further from their mouth than in normal conversation and will be more numerous. That said, it doesn't account for the results of a simulation study published by scientists at the Eindhoven University of Technology in the Netherlands. There they saw that the air behind runners and bicyclists could be contaminated over a significant distance. While droplet transmission wouldn't account for the study's results, aerosol transmission readily explains it.

Aerosol transmission considerations significantly alter basic strategy considerations to prevent the transmission of COVID-19 compared to droplet transmission.

Aerosol transmission leads us to consider some different strategies than droplet transmission. It forces us to carefully consider the number of people that should be allowed in a room as well as how close each is from the others. It means we should consider ventilation issues whenever inside as well as air filtration. Finally it leads us to think about critical prevention of halting aerosol and droplet exhalation to the extent possible.

COVID-19 infection can occur by touching contaminated surfaces.

COVID-19 infection can occur by touching contaminated surfaces, then touching your nose, mouth, and possibly your eyes. The CDC states,

“It may be possible that a person can get COVID-19 by touching a surface or object that has the virus on it and then touching their own mouth, nose, or possibly their eyes. This is not thought to be the main way the virus spreads, but we are still learning more about this virus.”

Too many interpret that statement to mean that we shouldn't worry about contaminated surfaces. What the CDC is saying is that we need to worry about person-to-person contact more than any other manner of becoming infected. Therefore, we need to “mask up” and wash our hands. In addition, the CDC directs us to “routinely clean and disinfect frequently touched surfaces.”

To understand about potential COVID-19 transmission from various surfaces, such as we find on camera gear, we need to understand how the virus behaves on the materials used to make the gear.

COVID-19 (SARS-CoV-2) studies to determine its viability on surfaces have been completed by scientists from the National Institute of Allergy and Infectious Diseases, Princeton University, UCLA and the CDC. They published their findings in the prestigious New England Journal of Medicine.

They found that COVID-19 was viable on plastic surfaces for up to 72 hours (half-life < 7 hrs.), on stainless steel surfaces for up to 48 hours (half-life < 6 hrs.), on copper for 4 hours (half-life = ~1 hr.), and on cardboard for up to 24 hours (half-life < 4 hrs.).

No studies of the viability of COVID-19 on fabrics are complete, but since the studies on other surfaces show that COVID-19 and SARS are similar, infectious disease experts such as Dr. Amesh A. Adalja of the Johns Hopkins Center for Health Security believe that COVID-19's viability on fabrics is from “several hours to maybe a day.”

Time is a critical COVID-19 infection factor.

Time is a critical factor in COVID-19 transmission and spread. For example, if we come in contact with an infected person for a very short time, such as if they pass us on the street, or if they're behind a checkout counter, we don't have a high likelihood that they will transmit the disease to us. On the other hand, we would have a higher likelihood of becoming infected in a restaurant, regardless of sitting inside or outside, if our server is infected with COVID-19. That's because over the course of 45 minutes to several hours, the server would often be physically close and handling much of what we touch. In a hair salon type setting, with an infected stylist, the likelihood of becoming infected is higher yet. That's because for a half hour to 45 minutes, the stylist works just inches from us most of the time.

Of course, in each case, if the infected person was wearing a mask, and we washed our hands before touching our mouth, nose and eyes, that would reduce the likelihood that we would become infected.

If we touch an COVID-19 contaminated surface within an hour of its contamination, then touch our face, particularly our nose, mouth and eyes, as the virus is most viable at that point, transmission of the virus to us has a reasonable likelihood, particularly with multiple touches. On the other hand, if we touch the contaminated surface hours later, we're less likely to become infected than shortly after its contamination.

That's because COVID-19 degrades exponentially. Scientists found that while COVID-19 can remain viable on surfaces like polycarbonate camera gear cases for up to 72 hours, it initially degrades rapidly soon after contamination, then more slowly degrades until it's no longer viable. The virus half-life is less than 7 hours. So, in less the 10 percent of the time the virus could remain viable, its viability is already cut in half.

By taking into account what we know about COVID-19 transmission, we can devise a reasonable and effective strategy to keep us and those around us as safe as possible, while we're photographing the people and scene before us. Soon, in Part 2, A COVID-19 strategy for photographers, I'll discuss what safety measures photographers can use for COVID-19 protection paying attention to both primary and secondary transmission methods of the virus.

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