- Andre Beernas
- BBC News, Brazil
5 hours ago
After two and a half years of the new coronavirus infection (COVID-19) pandemic, the number of infected people is increasing worldwide again. Let’s look at how the coronavirus affects the human body and what happens after first contact with the pathogen.
With the spread of BA.4 and BA.5, which are sub-variants of the Omicron mutant virus, which have strong infectious power, and various quarantine measures are being eased, the number of confirmed cases of Corona 19 is increasing.
In this situation, new questions are raised about how the human body is infected with the coronavirus and how it is affected.
The timeline below is an average estimate based on studies reviewed by international health organizations and is subject to change.
Day 0: Infection
You become infected after coming into close contact with someone who is already infected with the coronavirus.
When an infected person talks, sings, coughs or sneezes, they excrete tiny droplets that carry coronavirus particles. The amount of virus it contains is significant.
“Some people only have about 10,000 viruses per ml of droplet,” says José Eduardo Levy, a virologist at the University of São Paulo Medical Research Institute in Brazil. “I’ve seen cases where dogs have been found,” he said.
These small droplets of the virus either hit the face of someone nearby, or “float” in the air for minutes or even hours.
It can be compared to cigarette smoke in a room, and depending on the air circulation conditions of each place, you inhale these aerosols with your breathing apparatus.
This is when the infection starts.
The Severe Acute Respiratory Syndrome Coronavirus Type 2 2 (SARS-CoV-2), which caused the COVID-19 pandemic, binds to cell receptors in the mucous membranes of our nose, mouth and eyes through a protein spike on the outer surface and penetrates into cells. .
It then infects the human body by pushing its own genetic material into the cells and reproducing itself.
Dr. Levy estimates, “A single cell typically produces between 100 and 1000 replicating viruses.” “The cells are replicating so much that they can’t cope. When the cell bursts and eventually dies, the virus is released and attaches itself to the surrounding cells and repeats the same process. repeat ,” he added.
The large-scale prevalence of these viruses is also associated with new mutant viruses. Viruses cannot replicate their genetic information as they are, and mutations with large genetic mutations appear in the process.
However, if these genetic mutations are favorable to the survival of the virus, new mutated viruses such as alpha, beta, gamma, delta, and omicron, which we are familiar with, are active.
Days 1-3: Breeding period
The coronavirus, having penetrated the first cells of the human body, is now expanding its field of activity.
The virus expands its territory within the host as it releases thousands of replicating viruses from each cell it attacks. However, as it cannot detect that the virus is replicating and multiplying, this period is known as the ‘latent period’.
Anderson F. Brito, a virologist at the Todos Pella Saud Institute (ITpS), a non-profit organization that researches infectious diseases in Brazil, said, “We found that the incubation period of the new mutant virus is shortened.”
The UK Health and Safety Agency report also states that the incubation period for alpha mutations is 5-6 days on average, while the incubation period for delta mutations has been shortened to 4 days.
In the case of the Omicron mutation, the incubation period from virus spread to onset of symptoms was further reduced to an average of 3 days.
This means that it used to take almost a week for typical symptoms to appear after a coronavirus infection, but now it can develop almost overnight.
However, the incubation period can vary, with some experiencing first symptoms just 14 days after first contact with the virus.
Days 4-14: Symptoms start and get worse
As the virus spreads to the upper respiratory tract (nose, mouth and throat), the body’s immune system is stimulated to counterattack.
The first line of defense is lined with what are known as ‘natural killer cells’ such as neutrophils and monocytes. Details of this can be found in a paper published last year by two researchers from Zhejiang University Hospital in China.
Over time, a slightly different defense begins to work. That is, T lymphocyte cells (T cells), which elicit a more systematic response to virus invasion, and lymphocyte cells (B cells) which produce antibodies to antigens, come forward.
Symptoms of corona infection, such as runny nose, cough, fever, and sore throat experienced by some infected people, are a result of this immune response. It is a phenomenon that occurs when a very large number of cells work constantly to eliminate viruses in the body.
But how long will these symptoms last?
Professor Nancy Belay, an infectious disease and virology specialist at the University of São Paulo, said, “There is a lot of individual variation.
Professor Belay, who is also a member of the Brazilian Society of Infectious Diseases (SBI), predicts that “In general, the worst symptoms, such as sore throat or fever, last for about three days.” It can last for ~10 days,” he added.
At this time, it is important to isolate and avoid contact with others as much as possible. If you go out or meet other people, you can prevent the virus from spreading by wearing an appropriate mask.
From a collective perspective, isolating the infected is important to break the chain of virus transmission in the community and to stop the increase in the number of confirmed cases.
In case of infection, you need to rest and hydrate well to recover quickly. Medications such as antipyretics and pain relievers may also be helpful.
“If you have shortness of breath or a fever persists after 72 hours from the onset of symptoms, it is best to see a doctor,” advised Professor Belay. This is especially true for the elderly, patients with chronic diseases, and patients with weakened immune systems.
After Day 15: End (or start of ‘long covid’ symptoms)
About two weeks after the first contact with the coronavirus, the body’s immune system usually “wins the battle”, stopping the process of replicating and destroying cells.
And vaccines helped them win. That’s because the vaccine allows the immune system to be safely “trained” before it actually comes into contact with the virus.
Unfortunately, sometimes the virus can spread to large organs (such as the lungs) and cause severe inflammation. This usually requires urgent treatment and increases the risk of death.
However, even in patients who have recovered well, there is a risk of ‘long covid’, where symptoms persist for months (or years).
There is still a lot of uncertainty about this, but the Centers for Disease Control and Prevention (CDC) estimates that up to 13.3% of people infected with the coronavirus will complain of symptoms that last more than a month. And in about 2.5%, the symptoms lasted for at least 3 months.
According to the CDC, more than 30% of those infected with Corona, who had to go to the hospital at the time of infection, still experience discomfort such as fatigue, shortness of breath, anxiety, and joint pain even after six months.
Regarding the ‘long covid’, the CDC said it is working to understand more about what causes it and why it is reported more often in certain populations.