The President of the Russian Federation invited the regions to develop measures for a gradual exit from the regime of self-isolation. Not so long ago, quarantine restrictions began to be lifted in various US states. Similar situations raise similar questions and concerns. Will there still be a risk of infection after lifting the restrictions? How safe is it now to go to the office, to the store, visit a restaurant, use public transport, talk with someone on the street? We present to your attention a translation of an article by an American biologist Erin Bromage (Erin Bromage), in which he examines these problems in detail, with examples, and answers these questions.
Many people seem to sigh with relief, but I don’t know why. The epidemic curve has a relatively predictable rise, and as soon as it reaches a peak, the descent can also be predicted. We have reliable data on outbreaks in China and Italy, which show how the number of deaths is slowly decreasing, but mortality persists for several months. If the peak fell on 50 of thousands of deaths, it is possible that over the next six weeks, until the curve decreases, we will lose more 50) person. And this is subject to quarantine.
As the states open, the virus will receive more fuel, which means that forecasts will lose relevance. I understand why there is a desire to restart the economy, but, as I said earlier, if the biology issue is not resolved, the economy will not recover.
Only a few states show a steady decline in the number of new infections. Indeed, as of May 3, the majority of patients is growing, but they remove quarantine. Let me give you a simple example of a trend in the United States: if you exclude data for New York and look at the rest of the United States, it turns out that the number of new cases per day increases. Bottom line: the only reason the graph of the total number of new cases in the United States now seems to be even is that the epidemic in New York was very large, but now it is under control.
Thus, in most of the US, we will add oil to the viral fire, removing the restrictions. This will happen independently of me, so the goal of my post is to help you avoid excessive risks.
Where do people get sick?
We know that most people become infected at home. Household members become infected with the virus in society and bring it home, where constant contact between household members leads to infection.
But how do people get infected in society? I regularly hear people worried about grocery stores, bike rides, irresponsible runners without masks ... Is that cause for concern? Not really. Let me explain.
In order to get infected, you need to get an infectious dose of the virus. Based on studies of infectious doses with MERS and SARS, some believe that infection requires everything 900 SARS-CoV-2 virus particles. Note that this still needs to be determined experimentally, but you can use this number to demonstrate how infection can occur. You can become infected by inhaling once 760 viral particles or just rubbing your eyes or inhaling times by 92 virus particles, or 90 inhaling once . Each of these situations can lead to infection.
How much virus enters the environment?
Restrooms: in the latrines there are quite a lot of surfaces that people often touch - door handles, faucets, entrance doors. Thus, the risk of transmission of the virus through surfaces in this environment can be high. It is still unknown whether fecal virus is released or only its “debris”, but it is known that flushing the toilet leads to aerosolization of many drops. Be especially careful in public toilets (both with surfaces and with air) until more data appears.
Cough: when a person coughs once, he gives out about 1140 drops, and the drops spread with speed 31 miles per hour (70, 5 km / h). Most drops are large and quickly settle (due to gravity), but many remain in the air and can cross the room in a couple of seconds.
Sneezing: when a person sneezes once, it highlights about 20 drops, while the drops move at a speed of up to 99 miles per hour (200 km / h). Most drops are small and spread over long distances (across the room - with ease).
If a person is infected, drops from one cough or sneezes may hold up to 100) (two hundred million) virus particles that may be in their environment.