As the lock down eases and we are allowed to go back to our workplaces, being in contact with more people in more places more regularly increases the risks to ourselves and our families. Studies show that if a person coughs or sneezes, they release about two hundred million viral particles everywhere. Some virus hangs in the air, some falls into surfaces, most falls to the ground. So if you are face-to-face with a person, having a conversation, and that person sneezes or coughs straight at you, it is possible to inhale 1,000 virus particles and become infected.
But even if that cough or sneeze was not directed at you, some infected droplets–the smallest of small–can hang in the air for a few minutes, filling every corner of a modest sized room with infectious viral particles. All you have to do is enter that room within a few minutes of the cough/sneeze and take a few breaths and you have potentially received enough virus to establish an infection.
Speaking increases the release of respiratory droplets about 10 fold; about 200 virus particles per minute. Again, assuming every virus is inhaled, it would take about five minutes of speaking face-to-face to receive the required dose.
If you spend about ten minutes talking face-to-face with an infected person you are potentially infected. Anyone who shares a space with you for an extended period is potentially infected.
This is also why it is critical for people who are symptomatic to stay home. Your sneezes and your coughs expel so much virus that you can infect a whole room of people.
How much virus is released into the environment?
Bathrooms have a lot of high touch surfaces, door handles, faucets, stall doors. So fomite transfer risk in this environment can be high. We still do not know whether a person releases infectious material in feces or just fragmented virus, but we do know that toilet flushing does aerosolize many droplets. Treat public bathrooms with extra caution (surface and air), until we know more about the risk.
Symptomatic people are not the only way the virus is shed. We know that at least 4 per cent of all infections–and the majority of community-acquired transmissions–occur from people without any symptoms (asymptomatic or pre-symptomatic people). You can be shedding the virus into the environment for up to five days before symptoms begin.
Infectious people come in all ages, and they all shed different amounts of virus. The amount of virus released from an infected person changes over the course of infection and it is also different from person-to-person. Viral load generally builds up to the point where the person becomes symptomatic. So just prior to symptoms showing, you are releasing the most virus into the environment.
You need to look at your environment and make judgments. How many people are here, how much airflow is there around me, and how long will I be in this environment. If you are in an open floor plan office, you really need to critically assess the risk (volume, people, and airflow). If you are in a job that requires face-to-face talking or even worse, yelling, you need to assess the risk. If you are sitting in a well-ventilated space, with few people, the risk is low.
If you walk past someone who is infected, you need to spend a minimum of five minutes breathing in their air to become infected. While joggers may be releasing more viruses due to deep breathing, remember the exposure time is also less due to their speed. Please do maintain physical distance, but the risk of infection in these scenarios are low. Do your part and wear a mask to reduce what you release into the environment. It will help everyone, including your own business. If you don’t solve the biology, the economy won’t recover. Wash your hands often and stop touching your face!