Symptoms, transmission, double infection: what we know about Covid-19

How do you know if you have coronavirus? How to catch it? Can we be infected twice? France 24 provides an update on the latest information known about this new coronavirus: bine now known as Covid-19.

• What are the symptoms of this virus?

If you have breathing problems, fever, cough, or are short of breath or have difficulty breathing, you are potentially affected by Covid-19. These symptoms listed by the World Health Organization (WHO) may be more or less present depending on the case. Evolution can also be fluctuating, with ups and downs.

Another common symptom is loss of smell and taste. According to a recent Belgian study carried out on 417 patients who were "non-severely" infected, 86% presented with smell disorders (most of them no longer smelling anything) and 88% with taste disorders. In general, symptoms last two weeks, sometimes longer, sometimes less. And the aggravation can occur in a second time.

"In the most severe cases, the infection can lead to pneumonia, severe acute respiratory syndrome [SARS], renal failure, or even death," said the WHO.

There is no vaccine or medication, and management involves treating the symptoms. However, some patients are administered antivirals or other experimental treatments, the effectiveness of which is being evaluated.

In addition, one can be a carrier of the virus, without having the symptoms (one says then that the patient is "asymptomatic"). Hence the need, without being tested, to leave your home only when necessary.

• What modes of transmission?

The virus is mainly transmitted by respiratory route and by physical contact. Transmission by respiratory route occurs through the droplets of saliva expelled by the patient (symptomatic or asymptomatic), for example when he coughs. Scientists believe that this requires a close contact distance (about one meter, even 1.50 meters).

To avoid contagion, health authorities emphasize the importance of barrier measures: avoid shaking hands and kissing, washing hands frequently, coughing or sneezing in the crook of one's elbow or in a disposable handkerchief , wear a mask (whether you are sick or not) ... In addition, you can become infected by touching an infected object, then putting your hand to your face (eyes, nose, mouth ...). It is therefore very important to wash your hands regularly.

A study published in mid-March in the American journal NEJM showed that Covid-19 can be detected for up to two to three days on plastic or stainless steel surfaces, and up to 24 hours on cardboard. However, these maximum durations are only theoretical, since they are recorded under experimental conditions.

"Just because a little virus survives does not mean that it is enough to infect a person who touches this surface. Indeed, after a few hours, the virus [for the most part] dies and is probably not more contagious ", underline the French health authorities on the official government website on coronavirus.

Another unknown: the ability of Covid-19 to be transmitted via expired air ("aerosols" in scientific jargon) and not just coughing or sneezing. The subject of much speculation in recent weeks, this mode of transmission is not yet scientifically proven.

• Can we be infected twice?

Is it possible to be infected with the coronavirus, to heal, to be tested negative, and then to be reinfected in stride? A few cases in Asia have raised this question. Since these cases were isolated, scientists believe they are due to the fact that these patients never really healed. The negative test can either come from the fact that it was poorly done, or from a very weak presence of the virus in the body. However, we still lack certainty about the immunity we can acquire against the virus.

Based on the example of other viral diseases, specialists believe that once cured, one is temporarily immune, even if this is not yet proven. However, the duration of this supposed immunity is unknown. This question is crucial.

"If a person can in theory be immunized for a long period, for example 12 to 24 months, then he can return to public places safely, even if the virus is still circulating […] Conversely, if the "Immunity is very short, a person who has already been infected could be infected again very soon after healing," says the Center for Strategic and International Studies (CSIS) in Washington.

• Who are the people most at risk?

The severity of Covid-19 and the disease caused by this new coronavirus increases with age, as various studies have shown. Published on March 31 in the British medical journal The Lancet, the latest shows that the disease is on average much more formidable for people over 60 years, with a mortality rate of 6.4% (among confirmed cases ).

The mortality rate even climbs to 13.4% for those over 80 years of age compared to 0.32% of deaths only for those under 60 years of age, according to this work mainly focusing on several hundred Chinese cases observed in February. Similarly, this study shows that the proportion of patients requiring hospitalization increases sharply with age: 0.04% for 10/19 year olds, 4.3% for 40/49 year olds, 11.8% for 60 / 69 and 18.4% for those over 80. The latter figure means that about one in five octogenarians develops a form serious enough to require hospitalization.

Besides age, having a chronic illness (respiratory failure, cardiac pathology, history of stroke, cancer, obesity ...) is a risk factor, this is called comorbidity factors . In a recent report on 10,000 deaths, the Italian Higher Institute of Health (ISS) identified common pathologies in the deceased. The most common are hypertension (73.5% of cases), diabetes (31%) or ischemic heart disease (a serious heart condition, 27%).

Finally, according to a large analysis published on February 24 by Chinese researchers in the American medical journal Jama, the disease is mild in 80.9% of cases, "serious" in 13.8% of cases and "critical" in 4, 7% of cases.

• How many deaths should we expect?

If one relates the number of deaths in the world to the total number of officially registered cases, Covid-19 kills approximately 5% of the patients diagnosed, with disparities according to countries. But the supposed fatality rate has to be taken with caution, as it is not known how many people have actually been infected. Since many patients seem to develop few or no symptoms, their number is likely to be greater than the cases detected, which would therefore lower this rate.

In addition, countries have very different testing policies and some do not systematically test all suspected cases. In reality, if we integrate an estimate of undetected cases, "this probably gives a mortality rate around 1%", or "10 times more than the seasonal flu", explained a few weeks ago the American Anthony Fauci, director of the National Institute of Infectious Diseases, before Congress.

The study published in The Lancet on March 31 estimated the proportion of deaths among the confirmed cases at 1.38%. However, the danger of a disease does not only depend on the absolute death rate but also on its ability to spread more or less widely.

Even if only 1% of patients die, "it can make significant figures if 30% or 60% of a population is infected," said Dr. Simon Cauchemez, of the Institut Pasteur in Paris.

The other factor that aggravates the mortality linked to this new disease is the congestion of hospitals due to a massive influx of cases. This complicates not only the management of patients with severe forms of Covid-19, but also that of all others.

With AFP

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