definition, origin, when is it contagious?

Caused by the Sars-CoV-2 coronavirus, Covid-19 is a highly contagious disease. Controversial origin, incubation, mutation, relapse, treatment, transmission: an update on current scientific knowledge.

[Mise à jour le mardi 5 mai 2020 à 18h28] At the end of 2019, grouped cases of pneumonia occur in China, some of which are fatal. On January 9, virus responsible is identified, it is a new coronavirus called SARS-CoV-2. In May, this highly contagious virus spread over the 5 continents of the Earth and has contaminated more than 3.5 million people in more than 187 countries, out of 198 in total, causing 247,000 deaths. What do we know about him today?

After being baptized nCoV-2019 at first, this new coronavirus was called SARS-CoV-2 (SARS for “Severe Acute Respiratory Syndrome” and CoV for “COronaVirus”). His illness was named Covid-19 February 11, 2020 by the WHO to mean:

• “Co “means” corona “,
• “vi” for “virus” and
• “D” for “disease” (“illness” in English).

The number 19 indicates the year of its appearance: 2019. “We had to find a name that did not refer to a geographic location, an animal, an individual or a group of people” said WHO Director-General Dr Tedros Adhanom Ghebreyesus to avoid stigmatization of the disease. The Minister of Health Olivier Véran announced Tuesday April 21 before the National Assembly that the Covid-19 would be recognized “automatically” as occupational disease for all nursing staff, regardless of their place of practice, in town, in the hospital or in a nursing home.

SARS-CoV-2 belongs to the family of coronavirus (with a large number of viruses) which can cause mild illnesses in humans such as colds and more serious pathologies as the Sras. Since the beginning of the epidemic, the track of animal contamination is the most plausible according to scientists. The epidemic is part of a Wuhan local market in China where were sold animals wild. Currently, it is still unclear which animal is responsible for it. It could be the bat where a virus very similar to Sars-CoV-2 was detected. On February 7, 2020, scientists from the Southern China University of Agriculture identified the pangolin as a “possible intermediate host” suspected of having transmitted the coronavirus to humans. This small mammal consumed in southern China could be implicated as intermediate host between the bat and humans. The pangolin is a mammal covered with scales threatened with extinction, whose delicate flesh is highly prized in Chinese and Vietnamese gastronomy. In a press release, scientists explain that an animal can carry a virus without being sick and transmit it to other species such as humans. After analyzing 1,000 samples, scientists were able to show that the genomes of virus sequences taken from pangolins were 99% identical to viruses found in people with nCoV, says Chine Nouvelle. Recall that during the 2002-2003 SARS epidemic, the intermediate host of the virus was the civet, a small animal with a gray coat whose meat is eaten in China. The bat was also responsible for the transmission of viruses to humans, including SARS, MERS in Saudi Arabia, and also Ebola. However, on April 17, Pr Luc Montagnier, Nobel Prize in Medicine in 2008, questioned by Pourquoi Docteur refutes this hypothesis of contamination. According to him, the new coronavirus was manufactured in Wuhan laboratories : “The Wuhan city laboratory has specialized in coronaviruses for a very long time (…) they have expertise in this field” he recalls. Professor Montagnier looked at the description of the coronavirus genome: “The complete genome of this new coronavirus had sequences from another virus which is HIV, the AIDS virus. This was published by Indian researchers who were forced to retract. There is tremendous pressure to bring the truth out. ” To insert an HIV sequence into the genome you need molecular tools, it cannot be linked to a natural mutation, explains the scientist. “The assumption is that this virus leaves the laboratory of Wuhan, (…) the history of the fish market is a beautiful legend” he believes. The US said May 5 hold “evidence” that it came from a laboratory in Wuhan, and President Donald Trump threatened Beijing with “punitive customs taxes“But the WHO remains cautious: “We have only received no specific US government data or evidence regarding the suspected origin of the virus, so for us it remains speculative “, said Michael Ryan, WHO director of emergency programs, at a virtual press conference. On May 1, WHO assured the new coronavirus was “naturally occurring”, according to many scientists, and not made by humans. An opinion shared by Dr Olivier Schwartz of the Institut Pasteur : “In the laboratory, we can manipulate certain viruses to modify some of their components but we cannot create a new virus by mixing two viruses of different species. We cannot create a coronavirus taking an element of HIV and another virus“ he said on RTL.

“For the moment, none of the mutations identified can be associated with increased virulence”

The genetic sequence of the Sars-CoV-2 virus was decrypted on January 10. According to the latest scientific data, there are two circulating strains of the virus (L and S).

• The S strain is said to be older than the L strain. At this stage, there is nothing to confirm whether the mutation took place in humans or in intermediate hosts (animals).
• The L strain would be the most severe and frequent circulating strain (70% of the samples tested in the study), while the S strain would be less aggressive and less frequent (30% of the samples).

“Thanks to the means of detection and the measures to combat the coronavirus, the circulation of the L strain, more severe and therefore more easily detectable, tends to decrease” indicates the government on its site. Regarding the mutation of the virus, scientists are not worried. On April 30, Professor Arnaud Fontanet explained that “The virus does not mutate very surprisingly when it has just emerged in humans and for the moment none of the mutations identified can be associated with increased virulence or with increased transmissibility”.

To know : If the mutation of the virus worries, Dr. Gérard Kierzek reminds us that it is not necessarily more dangerous for humans: “The mutation can go both ways, towards more virulence or less virulence, more contagiousness, less contagiousness.”

Unlike the flu that comes on suddenly, a coronavirus infection “is done gradually over several days” says the Pasteur Institute. Patients report symptoms that appear over a week and a fairly long healing time. “In more than 80% of cases, the signs are quite minor. They are angina or nasopharyngitis” indicated Professor Karine Lacombe, head of the infectious diseases department at the Saint-Antoine hospital in Paris, during a press conference on television on March 28, 2020.

The WHO distinguishes several clinical syndromes associated with SARS-CoV-2: uncomplicated disease, mild pneumonia, severe pneumonia, ARDS (acute respiratory distress syndrome), sepsis and septic shock. In the most serious cases Covid-19, which require medical treatment: respiratory signs (difficulty breathing which can lead to acute respiratory distress syndrome that is, a failure in respiratory function).

In children: cough or shortness of breath associated with any of the following signs: cyanosis, acute respiratory distress (whining), signs of pneumonia with an alarm sign: unable to drink or breastfeed, loss of consciousness or seizures. Several cases of inflammatory syndromes have been reported in Paris in late April-early May, with symptoms close to Kawasaki disease, in children who were infected about a month earlier by Covid-19.

To monitor your temperature if you think you have been infected with the coronavirus, the Ministry of Health recommends:

• take your temperature every day, morning and evening, using a thermometer reserved for your personal use,
• then note the date, time of measurement and temperature on the attached sheet,
• use the same method to measure your temperature every day.
• take your oral temperature as follows: place the thermometer under the tongue ensuring good contact with the tongue, close your mouth tightly and breathe gently through your nose, leave the thermometer in place for about 45 to 90 seconds, or until the thermometer indicates that the measurement has been made if you are using an electronic thermometer (often indicated by a beep), note the measured temperature and the date and time of the measurement, • clean the thermometer with cotton wool soaked in alcohol modified at 90 °.

The average incubation time is 4 days with a maximum duration of 12 to 14 days.

The peculiarity of the new coronavirus, in comparison to SARS, the Mers virus or that of the flu, is its strong contagion. “The SARS coronavirus was contagious only a few days after the onset of symptoms, 4 days later. This left time to diagnose and isolate the patients before they contaminated other people. With SARS, all the patients had severe forms so they were all identified, we did not miss benign forms which could have been unnoticed. With this coronavirus, contagion begins with the onset of symptoms and sometimes in people who do not have symptoms” explained Professor Arnaud Fontanet, epidemiologist at the Institut Pasteur during a round table in the Senate on February 26, 2020.

→ Contagion for several weeks : Another fact noted during the epidemic by caregivers, the duration of contagion of this new coronavirus which can go up to a month in certain patients, as indicated by professionals on the Collective Inter-intensive care on Facebook. “Some of our patients are still positive after more than 3 weeks of resuscitation” says one of these caregivers.

→ A more contagious virus than the flu: the transmissibility of SARS-CoV-2 is higher than that of seasonal influenza. The R0 (average number of people to whom a patient is at risk of transmitting the disease) is around 3 for this new coronavirus when it is only 1 for the seasonal flu. “With containment, we managed to reduce this number of reproduction to 0.6 so each patient infects less than one person which explains why the epidemic is declining “ explains Professor Fontanet on April 30 at a new Senate hearing. The new coronavirus is also very contagious because it is new and the population French has never faced it.

According to Dr. Gérald Kierzek, “after a fortnight when you have mild symptoms. Healing is spontaneous except when there is a severe form and you end up in intensive care where you need oxygen, where you have pneumonia and there we need to have medicine. Resuscitation patients stay in hospital for a long time, that’s more than 20 days. “

For Covid-19 patients who do not require hospitalization and which must therefore remain confined to the home, the High Council of Public Health specifies the containment lifting criteria to know : disappearance of fever and possible dyspnea from the 8th day after the onset of symptoms. It is also recommended to wear a mask for 7 days after recovery from contact with a person at risk.

Currently, according to the High Council of Public Health, a disappearance of fever and possible dyspnea from the 8th day after the onset of symptoms confirms the healing of the coronavirus. “After encountering a virus, our organism develops immune defenses called antibodies, allowing it to defend itself against this virus. After infection with the coronavirus, it is not yet clear whether these antibodies are effective and for how long. Although we are still at an early stage to decide on this question, in the opinion of scientists the first data seem reassuring, because today, no really confirmed case of re-contamination seems to have taken place“ explains the French government on its site. This is confirmed by the Director General of Health in France, Jérôme Salomon, on April 23 during a hearing before the National Assembly: “One, two, three weeks after an infection confirmed by a positive PCR test, antibodies gradually appear, this is the case in 99% of people who have been tested in different professional environments or in research protocols. These antibodies are protective which is reassuring. ” However, outside France, relapses have been reported. In South Korea, 91 patients considered to have recovered from the coronavirus have relapsed and again tested positive, As reported by Bloomberg. Jeong Eun-kyeong, Director General of KCDC (Centers for Disease Control and Prevention in Korea), says it is not a new infection but a virus reactivation in these patients diagnosed positive soon after quarantine. Virologists and epidemiologists have also stated that the virus COVID-19 may remain latent in certain cells of the body and attack the respiratory organs again once reactivated. Several cases of relapse have already been reported in Japan and China.

• In Japan, It was a woman in her forties working on a tourist bus who was diagnosed with the Covid-19 coronavirus for the second time, announced the government of the Osaka prefecture on February 27, 2020.

• In China, local media site Caixin reported on February 26 that 14% of patients discharged from hospitals in the southern city of Guangdong had tested positive for coronavirus in new tests.

The list of people at risk of severe form of Covid-19 was defined in the notice of March 31, 2020 and updated in the notice of April 20.

• people aged 65 and over (although people aged 50 to 65 should be monitored more closely);
• people with a history of cardiovascular disease (ATCD): complicated hypertension (with cardiac, renal and vascular-cerebral complications), stroke or coronary heart disease, cardiac surgery, NYHA III or IV stage * heart failure;
• the diabetics insulin-dependent or with complications secondary to their pathology. In diabetics, the Francophone Diabetes Society explains that the symptoms of Covid-19 do not differ: cough, fever, body aches, fatigue but also sometimes digestive signs. On the other hand, the infection will tend to unbalance the diabetes (just like during a flu). In the presence of a cough and a fever in a person with diabetes, the absence of significant imbalance of diabetes is a reassuring element rather going against COVID-19 – but imposing, in an epidemic situation, to stay at home . If there is an imbalance in diabetes, there is a significant risk of ketotic decompensation;
• people with chronic respiratory pathology likely to decompensate during a viral infection (obstructive pulmonary disease, severe asthma, pulmonary fibrosis, sleep apnea syndrome, cystic fibrosis in particular);
• patients with chronic kidney disease on dialysis;
• patients with active cancer under treatment (except hormone therapy);
• people with obesity (body mass index (BMI)> 30 kgm-2);

There is a lot of uncertainty today about the role that children can play in the transmission of the coronavirus.

Due to a suspected risk of serious Covid-19:

• people with congenital or acquired immunosuppression (medicinal product: anti-cancer chemotherapy, immunosuppressive treatment, biotherapy and / or corticosteroid therapy at immunosuppressive dose; HIV infection not controlled or with CD4 <200 / mm3; following a solid organ transplant or hematopoietic stem cells; linked to malignant hemopathy during treatment); *
• patients with stage B cirrhosis at least Child Pugh score;
• people with major sickle cell syndrome or with a history of splenectomy;
• pregnant women, in the third trimester of pregnancy, taking into account the available data and considering that they are very limited.

As with many infectious diseases, people with co-morbidities, suffering from chronic diseases (hypertension, diabetes), the elderly (over 70 years), immunocompromised or frail are at higher risk. In more severe cases, the disease can lead to death.

“We have a lot of uncertainty today about the role that children can play in transmission (from coronavirus), they have been little investigated as they do not have severe clinical forms and have not been hospitalized so there have been no studies. The only information we have is when we have had cases in families. When we look at the presence of the virus in these children without clinical manifestation, they kept the virus 6-7 days in the throat, they have the same viral loads as adults, we do not know if they are as contagious as them ” recalls Professor Arnaud Fontanet. For him, it is necessary distinguish the measures of deconfinement between children under 10 and adolescents. In China, a study published in the Jama February 24, 2020 showed that children under 10 years old represent 1% of cases, those between 10 and 19 years old 1% of 72,314 Chinese cases. Other international and French data confirm the mildness of the infection in children (severe cases and deaths are extremely rare but the cases of inflammatory syndromes close to Kawasaki disease identified in Italy and the United Kingdom should not be overlooked. -United Kingdom and in France). Children under 15 represent less than 1% of resuscitation admissions on April 5 in France and no child under 15 has died from COVID in France. A death occurred in a 16 year old adolescent girl (Santé Publique France). On its website, the French Pediatric Society believes that “children seem to be very little affected by this virus” but that they can “transmit the disease even if they are not very sick “. Hence the concern of many parents about the idea of ​​sending their children back to school on May 11.

Two publications on Covid-19 relate to pregnant women. The one published in the Lancet concerns 9 women, aged 26 to 40, with documented SARS-CoV-2 infection in the third trimester of pregnancy and no comorbidity. It did not show any particular gravity of the infection at the end of pregnancy and of a transmission to the fetus. The other also concerns 9 pregnant women (including 1 twin pregnancy) and reports the absence of difference in the clinical presentation of the infection.

There are two types of tests to diagnose Covid-19:

• the test called “by PCR” : to identify acute phase infection of the coronavirus. It is currently performed by a specific laboratory technique on a nasopharyngeal swab whose results can usually be obtained in 4 hours. No commercial test is available. There is :

• systematic sampling of the upper respiratory tract (nasopharyngeal / Virocult® swabs or aspirations)
• a sample of the lower respiratory tract (sputum, LBA, ATB) in case of parenchymal involvement.

• the serological test: that detects antibodies to Covid-19 in your blood and can tell if you have been infected in the past. These tests make it possible to detect in the serum the presence of antibodies of classes IgM and IgG specific for Sars-CoV-2. They use the method ELISA (enzyme linked immunosorbent assay) applicable on high throughput machines capable of performing hundreds of tests per day. They can be performed in most medical analysis laboratories. There are also rapid diagnostic orientation tests (TRODs) presented in a unitary format, detecting antibodies from a single drop of blood in minutes.

No treatment has proven its total effectiveness in combating SARS-CoV-2. Numerous clinical trials testing the efficacy of drugs against the coronavirus are in progress and listed by the WHO.

• In mild forms of the disease that do not require hospitalization: in case of fever, it is advisable to take paracetamol and not anti-inflammatory drugs which can make the infection flare up. Watch for symptoms and if it gets worse with difficulty breathing, call 15.
• As soon as the infection requires a use of oxygen therapy (including low-speed) hospitalization is required. In the presence of signs of severity, a treatment can be considered: use of an antiviral drug (combination lopinavir ritonavir, or even Remdesivir in the most severe cases) or, failing that hydroxychloroquine as indicated by the High Council of Public Health.
• In inflammatory forms with acute respiratory distress syndrome (ARDS), treatment options should be discussed on a case-by-case basis.

Discovery trial to test 4 combinations of drugs

A large trial called Discovery was also launched on March 22, 2020 on 3,200 Europeans affected by the coronavirus, including 800 French patients by Inserm, to analyze the effectiveness of five treatment formulas:

• standard care
• standard care plus remdesivir,
• standard care plus lopinavir and ritonavir,
• standard care plus lopinavir, ritonavir and beta interferon
• standard care plus hydroxy-chloroquine.

Five French hospitals are participating at the start (Paris – Bichat-AP-HP hospital, Lille, Nantes, Strasbourg, Lyon) then other centers to arrive at at least twenty participating establishments. In China, around twenty clinical trials are underway to analyze the effectiveness of this molecule in patients infected with SARS-CoV-2. Hydroxycholoroquine (a chloroquine analog) used to treat rheumatoid arthritis and lupus is also the subject of two trials in China in COVID-19 disease. In addition, antibiotic therapy is used in the event of pneumonia.

“This virus is more manufactured than we imagined at the beginning”

The new coronavirus is transmits between humans mainly through saliva, droplets (cough, sneezing), through close contact with patients (handshakes …). “He’s a lot more handcrafted than we imagined at the start” recognizes Professor Fontanet on April 30. He can too spread through contaminated surfaces (coronaviruses survive up to 3 hours on dry inert surfaces and up to 6 days in a humid environment). Regular hand washing (approximately every hour) and wearing masks help reduce the spread of the virus. “To slow the spread of the virus in the population, we therefore need avoid any proximity or contact with others as much as possible, install a virtual barrier between individuals, scrupulously refer to the instructions for barrier gestures: confinement at home, respect for the distance between individuals, frequent hand washing with soap or hydro-alcoholic gel. It is the only way to date to fight individually against the progression of the epidemic. It is our duty to do so “, warns Dr Patrick Aubé, general practitioner.

Transmission via stool

As indicated by the High Council of Public Health in an Opinion delivered on March 5 “SARS-CoV-2 can be found in body fluids including stool. However, the infectious nature of the virus detected in the stool in some cases is not proven and the risk of faecal transmission has not been documented” .

Animal transmission

There is currently no evidence that domestic animals such as dogs and cats can spread the virus and / or be infected by humans.

Water transmission : To date, no water contamination has been reported. “This disease is respiratory and probably animal to human, but the source has not yet been identified” explains the French government.

Covid-19 is a highly contagious disease. In the absence of truly effective treatments to counter it, prevention consists in respecting several barrier gestures.

• Vaccine: deadline, lines of work …

From the start of the coronavirus epidemic in France, researchers have been busy developing a vaccine against this highly contagious virus. According to the European Medicines Agency (EMA), such a vaccine should not not be available before 2021 Among the avenues envisaged, producing a vaccine from that of measles or BCG (tuberculosis).

Covid-19 has high mortality in adults. Between March 1 and April 28, 2020, 23,686 deaths of COVID-19 patients were reported to Public Health France: 92% of the cases of COVID-19 who died were 65 years of age or older. The median age at death was 84 years. The men accounted for 55% of these deaths. Comorbidities were reported for 65% of the death certificates received by Santé Publique France from March 1. Among these deaths, a mention of high blood pressure was indicated in 26% and 39% of the certificates contained a mention of cardiac pathologies.

According to the World Health Organization, Covid-19 is 10 times more lethal than H1N1, virus responsible for the influenza pandemic in 2009.

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