Healthy Covid carrier: test, antibody, are we contagious?

[Mis à jour le vendredi 4 décembre à 15h39] Among all those tested from 27 November to 3 December 2020, 72% said they were symptom-free, the same figure as the previous week. And half (50%) of the positive cases had no symptoms, according to Public Health France’s epidemiological point of December 3. Otherwise, half of the transmissions occur during the pre-symptomatic phase of the patient, therefore before symptoms appear. This means that you can be contagious even without symptoms. But exactly What does “being a healthy carrier” mean ? This is the file as an “asymptomatic” ? How do you know if you are a healthy carrier of a virus? During how long we are contagious ? Which is typical profile of a healthy Covid-19 carrier ?

A healthy carrier is a person whose body has been infected with an infectious agent (virus, bacteria, parasites) but showing no clinical signs of this infection. In other words, it carries the infectious agent into its system without being sick. Conversely, a healthy carrier can pass the infectious agent to other people with whom it comes into contact. A healthy carrier is therefore contagious.

To diagnose an asymptomatic person with Covid-19, we cannot rely on the presence of symptoms. So the only way to know if you are a carrier of Covid-19 (with or without symptoms) is to test for the presence of the virus, thanks to the realization ofa PCR test (a sample from the nose using a cotton swab) which allows to diagnose a possible contamination with Covid-19. If a person is infected with the coronavirus at the time of the sample, the PCR test will detect it.

• If the test is negative, we deduce that the person is not a carrier of the virus
• If the test is positive, it is deduced that the person is a carrier of the virus and is therefore contagious.

• If the positive person has no symptoms at the time of the sample, they are said to be a healthy carrier.

• If the positive person has symptoms (fever, cough, loss of smell, etc.), they are said to be symptomatic, is not a healthy carrier.

► Attention: There are “false negatives“may be due to poor sampling technique.

► Isolation for how long? With or without symptoms, a person who tests positive for Covid-19 must remain isolated for 7 days after testing.

The healthy carrier has no symptoms but remains contagious. It can then pass the disease on to other people. “In the case of Covid-19, this is especially true for children, adolescents or young adults“, specifies Frédéric Tangy, retired CNRS researcher, now assigned to the vaccine innovation laboratory of the Institut Pasteur in an article by Sud-Ouest. With or without symptoms, a person infected with Covid-19 can transmit the pathogen to 3 people on average, recalls the World Health Organization.

A healthy carrier would be less contagious than a person with symptoms.

The incubation period of Covid-19, that is the time between the moment of contagion and the appearance of the symptoms of a disease, is 3 to 5 days in most cases, but it can go up to 14 days. This means that an infected person can transmit the disease up to 3-14 days before symptoms appear (the average is estimated at 1 week). But since an individual can be a “healthy carrier”, there is always the risk of contagioneven after the incubation period. If not isolated, this person may unknowingly transmit the virus to others who may in turn develop a clinical, sometimes severe, form of the disease. Questioned by the 7.45pm broadcast on M6, Pr Yves Buisson, epidemiologist and chairman of the Covid-19 group of the National Academy of Medicine, indicates thatisolation allows us to consider that a healthy carrier is no longer contagious. But to get out of this isolation, the healthy carrier must take two negative samples to verify the absence of the virus.

However, a healthy carrier would be less contagious than someone with symptoms. since he does not cough and sneeze. “We wondered a lot if we could be contagious by being asymptomatic. Which is ultimately quite unlikely. Because to be contagious, you still have to expel the droplets, that is, cough, sneeze. So someone who certainly has no symptoms could be a carrier – this is very likely and from time to time we find them with extremely small symptomatic forms – but ultimately it has little means of spreading the virus“, indicates Jérôme Salomon, director general of health.

Nothing proves it. However, a first Covid-19 infection would lead to some form of protection dealt with the virus in the vast majority of cases, although around fifteen cases of reinfection have been reported worldwide, most notably in Hong Kong, the Netherlands, the United States and Belgium. Theoretically it would therefore be possible to be contaminated several times by the coronavirus. In addition, doctors have identified cases of patients who, after testing positive for Covid-19, then tested negative during a serological test, as if they did not develop antibodies or that these disappeared from the body between the two tests. “At the moment we still don’t have enough data on immunity to Covid-19 to draw definitive conclusions “, emphasizes Laurence Weiss, immunologist at the Georges-Pompidou European hospital, quoted in Liberation on 13 October.

In Singapore, a newborn had at birth, antibodies against the coronavirus, reports The Straits Time newspaper. This baby was born to a mother who was infected with Covid-19 during pregnancy in March 2020 on a trip to Europe. At the birth of the baby, “my pediatrician said the antibodies I had developed against Covid-19 were gone, but Aldrin [le bébé] had some. My doctor assumes I transferred my antibodies to him during pregnancy. ” An interesting case for scientists who still know little about the link between contamination and antibody development.

Coronavirus symptom reminder The first symptoms of the “new coronavirus” are not very specific : headache, muscle pain (stiffness), severe fatigue. Fever and respiratory signs (cough, respiratory failure, shortness of breath …) they occur later, often two to three days after the first symptoms appear. Loss of taste (ageusia) and loss of smell (anosmia) are now considered warning signs of a coronavirus infection.

A healthy carrier of a virus shows no clinical signs of infection:

• or because the infectious agent (virus, bacteria, etc.) is slightly virulent : the agent is too weak to cause body reactions and therefore symptoms.
• or why its immune defenses are very effective (develops more antibodies than average) and prevents the onset of symptoms.

You can be a healthy carrier of different viruses and diseases: chicken pox, flu, hepatitis B, tuberculosis, sexually transmitted diseases such as chlamydia, HIV (AIDS) and herpes …

We can also be healthy carrier of a gene as in the case of some genetic and therefore non-contagious diseases (Cystic fibrosis for example). In this case, the genes are passed from the parents to the child. Each child inherits half of their genes from their father and the other half from their mother. In France, more than two million people are believed to carry the cystic fibrosis gene without knowing it: this is called “healthy carriers”. They are at risk of passing the disease gene to their child without developing the disease, says Orphanet, the information portal dedicated to rare diseases.

These two concepts have more or less the same definition. A healthy carrier and an asymptomatic person were both infected but show no clinical symptoms associated with the infection. Small subtlety, however:

• We speak of a “healthy carrier” of an infectious disease (healthy carrier of a virus for example) or a genetic disease. On the other hand, we cannot speak of a “healthy carrier” of a metabolic disorder (diabetes, arterial hypertension …).
• We speak of an “asymptomatic” person due to an infectious disease, a genetic disease or metabolic disorders.

Second Public Health France December 3 report:

• 50% of coronavirus positive people show symptoms (data available for 53,533 cases) e 50% show no symptoms. This rate is stable compared to the previous week.
• 72% of people have tested coronavirus from November 27 to December 3 declared themselves symptom-free, a figure up slightly compared to the previous week (71%).

. Evolution of the number of confirmed cases of SARS-CoV-2 and of the positivity rate based on the presence or absence of symptoms (1,740,588 cases described), per week from week 23/2020, Metropolitan France (data as of December 2, 2020)

In June, Chinese researchers from the Infectious Diseases Department at Zhongnan Hospital in China wanted to learn more about the profile of people who were most likely to be asymptomatic. To do this, they analyzed the health status of 78 coronavirus-infected patients, 33 of whom were healthy carriers. Symptoms and signs, such as fever, fatigue, and dry cough, were monitored daily. At the end of their study published in the journal Jama Network, they found that asymptomatic people:

• They were on average 37 years old (compared to 56 years for symptomatic people)
• There were women 67% of cases. In other words, two out of three healthy carriers are women.
• Introduced less liver damage (liver) than in symptomatic people.
• It had a high rate of T helper lymphocytes (CD4 +: play an important role in the secondary immune response), “which suggests that the damage to the immune system was less than in symptomatic infections “, indicate the authors of the study.

Anyone can be a “healthy carrier” and can therefore participate in the spread of the disease without even realizing it. When in doubt, even if they don’t “feel bad”, each person should:

• Avoid any contact with vulnerable people (pregnant women, chronically ill, elderly, etc.).
• Do not go to places where vulnerable people are present (hospitals, maternity wards, accommodation facilities for the elderly, etc.).
• Respect the basic “barrier” gestures: wash your hands regularly (soap + water) or use a hydroalcoholic solution, cough or sneeze into your elbow or handkerchief, use disposable handkerchiefs (and throw them in the trash after first use). greet without shaking hands, without hugs and keep a distance of at least 1 meter from any interlocutor.
• Wearing a mask in confined spaces, but also outside the home, even in places where it is not mandatory
• Do a test for suggestive symptoms.

Source: COVID-19 quick summary. Share of asymptomatic forms and transmission of SARS-CoV-2 in the presymptomatic phase. Saint-Maurice: Public health France, 8 July 2020