The China Center for Disease Control and Prevention conducted a study of 72,314 confirmed, suspect, clinically diagnosed and asymptomatic cases of viral pneumonia seen on February 11. It is the largest study since the start of the epidemic.
In ten pages, Chinese researchers analyze the situation to monitor the development of the epidemic and draw a standard portrait of the patients. However, this work does not answer all of the questions, particularly concerning the mortality rate of the new Covid-19 coronavirus.
Here are the main findings of the study published by the Chinese Journal of Epidemiology.
The disease is “mild” in 80.9% of cases, "severe" in 13.8% of cases and "critical" in 4.7% of cases. People over the age of 80 are most at risk. Patients already suffering from cardiovascular diseases are the most threatened by a fatal outcome, above diabetics or people suffering from chronic respiratory diseases or hypertension.
There have been no deaths among children under the age of 10, though at least two babies have been infected in their mother's womb. Up to the age of 39 the mortality rate remains very low, then increases gradually with age. Men are more threatened than women by a fatal outcome.
Since the epidemic began in late December, epidemiologists and virologists have been intrigued by one fact: few children appear to have been infected. But it was very difficult to confirm this, since most of the data came only from adult hospitals.
This study therefore sheds new light: children indeed don’t seem to be significantly affected by the new coronavirus. Out of the 44,672 confirmed cases, barely 10% of the patients are under 30 years old and 2% are under 20 years old. Similarly, out of the 1023 deaths, only one person was between 10 and 19 years old and 7 between 20 and 29 years old.
The mystery is not yet resolved: we must now try to explain why. Several hypotheses are still valid. The new coronavirus may affect children less, for one reason or another. It could also affect them, but with extremely mild symptoms, which results in a lesser presence in hospitals.
The study confirms what we suspected from the start: the coronavirus is predominantly fatal for the elderly or those dealing with another pathology (comorbidity). Thus, if the number of infected is fairly well-distributed between the age groups from 30 years-old, the mortality rate is much higher from 60 years-old.
Especially since the infected patients listed by the Chinese authorities are certainly the ones presenting the most problematic symptoms. It is likely that many people affected by the coronavirus did not report to the hospital because the symptoms seemed mild.
The study takes stock of the development of what is today "a public health emergency of international concern". Going back to its appearance in the province of Hubei and following its spread to the rest of the country, this study presents in particular the periods during which China recorded the greatest number of cases.
Coronaviruses are a family of viruses that can cause a wide variety of diseases. In humans, they cause respiratory infections, ranging from a common cold to a severe lung infection, responsible for acute respiratory distress.
Two coronaviruses have led to serious epidemics in humans in the past: SARS-CoV responsible for a global SARS epidemic between November 2002 and July 2003, and MERS-CoV, identified for the first time in 2012 in the Middle East. East.
In early January 2020, a new coronavirus (SARS-CoV-2) was discovered in China. This new coronavirus has since caused a global epidemic (pandemic) of "coronavirus disease 2019", called COVID-19.
Coronaviruses have a viral envelope with a positive sense RNA genome and a kilobase capsid, incredibly large for an RNA virus. They rank among the Nidovirals, since all viruses of this order produce a nested set of subgenomic mRNAs during infection. Peak, envelope, membrane and capsid proteins contribute to the overall structure of all coronaviruses. These RNA viruses are single-stranded and positive-sense (group IV of the Baltimore classification). They can mutate and recombine2.
Bats and birds, as warm-blooded flying vertebrates, are ideal hosts for coronaviruses, along with bats and birds, ensuring the evolution and spread of the coronavirus3. Coronaviruses are normally specific to an animal taxon as host, mammal or bird depending on their species; however, these viruses can sometimes change hosts due to a mutation. Their human-to-human transmission occurs mainly through close contact via respiratory droplets generated by sneezing and coughing.
Coronaviruses were responsible for the serious epidemics of SARS from 2002-2004, the epidemic of MERS and the pandemic of Covid-19 in 2020. in humans serious epidemics of severe acute respiratory syndrome (SARS) in 2002 / 2003 and Middle East Respiratory Syndrome (MERS) from 2012, as well as the 2020 Covid-19 pandemic, caused by the coronavirus SARS-CoV-2. No vaccine or drug has yet been found to have proven effectiveness.
Like all viruses, the coronavirus is insensitive to antibiotics and bacteriophage preparations, which can only be useful against secondary bacterial infections.
In the case of SARS, drugs have been used to try to stop the epidemic: ribavirin, a nucleotide analogue, steroidal anti-inflammatory drugs and, after formal identification of the pathogen and sensitivity screens, alpha interferon and protease inhibitors. Their effectiveness is still questionable. None has been the subject of an adequate clinical study: many available studies do not allow clear scientific conclusions because they were carried out on small numbers of subjects or without protocol or fixed dose. Some even indicate that these treatments could have harmed the eradication of the virus42.
In the case of COVID-19, the treatment options include the administration of chloroquine or hydroxychloroquine, effective in vitro (laboratory tests) but toxic at high doses in vivo (in real conditions on humans). Studies in China and a therapeutic trial conducted at the Marseille University Hospital Institute by Professor Didier Raoult have shown some promise, but need to be extended and confirmed.