Covid-19: When are we most contagious?
A good friend recently called me (let’s call him John) for advice.
He had woken up with severe muscle aches and a great feeling of fatigue. Naturally, I was afraid I had contracted COVID-19, and called to ask me what I should do:
keep going to work, take a test as soon as possible or stay home. He didn’t know what to do because he had no other symptoms such as fever, cough, or breathing difficulties. Of course, it could be another type of respiratory infection, such as the flu or the common cold, but …
what if it was covid-19? What risk was there of infecting other people?
Coronavirus in Mexico, Covid-19
To find out when a COVID-19 patient is most contagious, our team of researchers developed a study
that was recently published in The Lancet Microbe.
We investigated three things: viral load (to measure the variation in the amount of virus in the body during illness),
viral shedding (the period of time in which someone expels the genetic material of the virus,
which does not necessarily imply that that person is infectious) and the isolation of the live virus
(which provides a better indicator of the contagiousness of a person since the live virus is taken, isolated,
analyzed and tested in the laboratory if it can continue to reproduce).
We found that viral load peaks in the nose ( thought to be the main route of transmission )
and in the throat during the early stages of infection. Specifically, between the first day with symptoms and the last. And this occurs even in patients with mild symptoms.
coronavirus sample procedure, Covid-19
We also found that, over several weeks, the genetic material of the virus can be detected in samples taken
from the throat and in stool samples. But no live virus was detected in any sample collected
nine days after the patient began to show symptoms.
However, some people, especially those who already suffered from serious illnesses or
who had weakened immune systems (from receiving chemotherapy, for example),
we’re likely to experience longer viral shedding processes.
In any case, the results suggest that those infected with SARS-CoV-2 have a propensity
to be contagious in the period between a few days before beginning to develop symptoms and the five days afterward.
A woman wearing chinstrap coughs in the street
In comparison, the SARS viral load peaks between 10 and 14 days after symptoms begin,
and MERS does so within 7 to 10 days (note that both SARS and MERS are diseases caused by a virus
that belongs to the coronavirus family).
This explains why the transmission of these two pathogens was effectively contained through the immediate localization and isolation of the people with symptoms.
And it also explains why it is being so difficult to contain COVID-19 since
it spreads very quickly in the early stages of the infection.
Contact tracing and simulations also show that the maximum level of transmission occurs in the first five days following the onset of symptoms
. According to a recently published study, the period of greatest contagion corresponds to those five days.
coronavirus public transport, Covid-19
Another contact tracing study carried out in the United Kingdom
and Taiwan similarly determined that most people were infected with the disease within
five days after the onset of symptoms by the contagionist.
Most of the people who take a test receive the results after the period of greatest contagion has passed.
The fact that the peak of viral load occurs at the beginning of the disease suggests that to break the chain of transmission,
a person with Covid-19 should be confined as soon as symptoms begin to appear,
without waiting for the results of the proof.
John immediately self-confined himself and called everyone he had had contact with within the previous days. The next day he woke up with a slight fever.
She was unable to get tested immediately, as she had to wait for an appointment, but she got the results on the fifth day after symptoms began.
Tested positive for Covid.
Luckily, John managed to isolate himself during the period when it was most contagious and his contacts immediately quarantined.
John was fortunate to the extent that he was able to work from home and therefore they continued to pay him.
But according to a report published in the UK, only one in five people can afford self-confinement.
Disabilities include having a dependent child in charge, having a low income,
the enormous financial hardships created by the pandemic, or being an essential worker, such as a nurse or teacher.
Governments could do more for Covid-19
How could the result of a test help you if your personal circumstances prevent you from confining yourself, if,
for example, you have a job that cannot be done from home, or if it does not allow you to take sick leave?
And of what use would these results be to you if your family depended on your salary,
or if your right to health care was tied to keeping your job?
coronavirus planet, Covid-19
These questions emphasize the fact that we must focus on helping people infected with
COVID- 19 so that they can self- confine in the early stages of the disease. Here we propose four forms of help:
1. Financial assistance so there is less pressure to go to work when you are sick.
2. Provide accommodation solutions to disadvantaged groups,
especially those who are in houses where many people live and also those who live with vulnerable people. This is a measure that has been carried out successfully in Vermont (United States).
3. Provide support services to people who are self-confined, as is done in New York and many countries in Southeast Asia.
4. Eliminate barriers to accessing health coverage and consider reducing quarantine periods
(reducing them to between five and seven days after symptoms appear ).
With this period, the days of greatest contagion could be covered and
it would make it easier for people to comply with the quarantine. Last September, France lowered the quarantine period to seven days, and Germany is considering lowering it even to five. The social benefits of reducing this period should outweigh any possible risk.
IF WE IMPLEMENT THESE MEASURES, WE WILL BE IN A MUCH BETTER POSITION TO DEFEAT THE PANDEMIC.