- Andre Bernath
- BBC World Service
Corona symptoms usually appear three days after contact with an infected person
Two and a half years after the outbreak of the epidemic, the number of infections with the Corona virus has risen again in different parts of the world.
This rise appears to be driven by several factors, the most important of which are the emergence of two new rapidly spreading subtypes of the omicron mutant (PA.4 and PA.5), and the easing of protective measures. This increase in infections raises new questions about the transmission and effects of the Corona virus on our bodies.
Let’s take a look at what the coronavirus does to our bodies, and what happens every day after the first exposure to the pathogen.
It is important to note that the following timeline is an average estimate based on information published in scientific studies reviewed by international health agencies. This schedule may vary in specific cases.
Day 0: infection
Infection begins after contact with a person who is already infected with the Coronavirus.
When a person talks, sings, coughs or sneezes, tiny droplets of saliva are released that carry coronavirus particles. The amount of virus varies greatly from person to person.
“Some individuals have a lower load, about 10,000 viral copies per milliliter of saliva,” says virologist Jose Eduardo Levy, an expert researcher at the Institute of Tropical Medicine at the University of São Paulo. We’ve seen people carrying up to a billion viral copies per milliliter.”
These small, infected droplets can be fired directly onto our face, or remain suspended ‘roaming’ in the air for minutes or even hours.
This dynamic is reminiscent of cigarette smoke in a room, and depending on the air circulation throughout, people may inhale this mist while breathing.
This is the time when the infection process begins and the virus uses the spike protein, which covers its outer surface, to connect to cell receptors in the mucous membranes of the nose, mouth and eyes.
picture released, Getty Images
Illustration showing coronavirus (in red) attaching to a cellular receptor (in green)
From that moment on, the virus begins to invade the cell and repeatedly uses its biological machinery to make new copies of itself.
Levy estimates that “this transcription process produces between a hundred to a thousand new viruses in one cell… This number is too high for the cell to deal with it… and after the cell explodes and dies, these viruses are released that repeat the same process in neighboring cells.”
This massive redundancy is also associated with the emergence of new mutations. Not all copies are identical, and some can have large genetic mutations. And if this genome change works in the virus’s favour, it opens the door to troubling new strains – such as the well-known alpha, beta, gamma, delta and omicron mutants.
Days 1, 2 and 3: Nursery
After the Corona virus has managed to invade the first cells in the body, the next step is to expand its field of action.
With each invaded cell releasing thousands of copies, the virus spreads more widely in the organism. This period of silent development, during which the virus cannot be detected, is known as incubation.
Virologist Anderson F. “We have noticed that the incubation time for the new variants has been reduced,” Prieto, research scientist at the Todos pela Saúde Institute in Brazil.
According to the report of the Health Security Agency in the United Kingdom, the incubation period for the alpha mutant lasted, on average, from five to six days, while in the mutated delta mutant, the incubation period was reduced to four days.
For the omicron mutant, the incubation period was reduced to three days.
In other words: Whereas typical symptoms of COVID-19 used to take nearly a week to appear, they may now occur overnight. But the incubation time may vary: in some cases, symptoms first appear 14 days after initial exposure to the virus.
Days 4 to 14: Symptoms appear and develop
As the virus advances through the upper airways (nose, mouth, and throat), it eventually catches the eye of our immune system, which then begins a counterattack.
The first line of defense includes cells such as neutrophils (a type of white blood cell), monocytes, and so-called “natural killers,” as detailed in an article published in 2021 by researchers at Zhejiang University Hospital in China.
Over time, other immune units play a role, such as T lymphocytes, which coordinate a more orderly response to viral invasion, and B lymphocytes, which release antibodies.
Symptoms of Covid 19 appear in some people as a result of this immune reaction: a runny nose, cough, fever and sore throat are simultaneous attempts to eliminate the virus by the body, which depends on the influence of many cells that work incessantly.
But how long do these symptoms last? Professor Nancy Bailey, an infectious disease specialist and virologist at the University of São Paulo says: “It depends a lot on each person’s immunity, and it varies from person to person. There are people who have few symptoms, and they actually recover after four or five days, while it takes time. Longer than others.
“In general, the worst symptoms, such as sore throat and fever, tend to last for about three days,” says Bailey, who is also a member of the Brazilian Society of Infectious Diseases (SBI).
“After this period, mild effects, such as a runny nose and cough, can last for seven to 10 days,” she says.
At this point it is important to stay isolated and limit communication with others as much as possible. And if you need to go out or interact with others, a good mask will avoid spreading the virus.
From a community health perspective, staying in isolation is essential to break the chain of transmission of the virus in the community, and to control the rise in cases.
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Corona virus is transmitted mainly through droplets coming from the mouth or nose of an infected person
Rest and continued fluid intake are essential to ensure recovery and give the body time to recover. Pain relievers and antipyretics can also help.
“If you feel short of breath 72 hours after the onset of symptoms, or the fever persists, it is recommended that you go to the hospital and seek medical attention,” Bailey says.
This is even more important for the elderly, people with chronic diseases, or those with weakened immune systems.
Day 15 and beyond: End (or appearance of symptoms of COVID-19)long last)
About two weeks after the first exposure to the virus, the immune system usually “wins” the battle and stops the process of cell multiplication and destruction.
Vaccines helped achieve this victory, as the doses allow the body’s defenses to safely “train” to fight the pathogen even before exposure.
Unfortunately, in some cases, the virus manages to reach vital organs (such as the lungs), leading to serious inflammatory conditions. These situations usually require emergency care, and present a high risk of death.
picture released, Getty Images
Some have more severe symptoms and need emergency care in an intensive care unit
Even for patients who have recovered, there is a long-term risk of contracting the coronavirus as symptoms persist for months (or even years).
Although long-term COVID-19 remains shrouded in mystery, the US Centers for Disease Control and Prevention (CDC) estimates that up to 13.3 percent of people infected with the coronavirus have long-term symptoms for a month or more. And about 2.5 percent reported symptoms that lasted for at least three months.
According to the Centers for Disease Control and Prevention, more than 30 percent of Covid patients who needed to go to the hospital had health problems six months after infection, ranging from fatigue and breathing problems to anxiety and joint pain.
The centers say they are studying more cases to learn and understand post-infection problems and their causes, including why some groups are more affected than others.