AFP, published on Saturday February 01, 2020 at 11:38 am
This is a meticulous investigation, which can potentially involve dozens of people: for each patient infected with the new coronavirus, we must find the people with whom he came into contact and make sure that they will not contaminate it. others in turn.
“The goal is to contain the epidemic by breaking the chains of transmission,” said Bruno Coignard, of the public health agency France, responsible for piloting these surveys in France.
They respond to “standardized protocols” and countries discuss them regularly, under the aegis of WHO. Internationally, the process has been prowled during other epidemics, Sras in 2002-2003, Mers in 2012-2013 and Ebola in 2014.
“Once a case is confirmed, the authorities work to identify (…) the people with whom he has been in close contact, to ensure that they are not likely to spread the infection”, says Dr. Bharat Pankhania, of the University of Exeter (England).
This is called “contact tracing”.
It all starts with an interrogation of the patient, to identify the people with whom he has been in contact since the onset of his symptoms (we assume that before, he was not contagious, even if it is one unknowns that remain at this stage).
Once these people have been identified, they are contacted by epidemiologists, who classify them according to three risk levels: zero / negligible, low, moderate / high.
The highest corresponds to “close contacts, face-to-face, within a meter, over a sufficiently prolonged period, 10/15 minutes”, according to Dr Coignard. This is for example the situation of a couple.
Conversely, the lowest level concerns caregivers who were well protected by their equipment, or people “who have very casual and stealthy contacts” with the patient. “If you see him on the street, there is no reason to have a transmission,” said Dr Coignard.
More difficult to gauge, belonging to the intermediate level, said to be weak, is left to the appreciation of the epidemiologist.
– Containment –
Instructions are then given to people according to their level of risk.
For the highest, they are asked to stay at home, take their temperature twice a day and report to health authorities if they have symptoms. Health authorities call them daily to ensure active follow-up.
In France, a compensation system is provided to compensate for the obligation to remain confined to the home.
People at the intermediate risk level should also take their temperature twice a day and report their symptoms or fever, but can go out.
For these two levels of risk, the follow-up lasts 14 days, the maximum estimated duration of the incubation period (the interval between the moment when you contract the virus and when you develop symptoms).
Finally, people whose risk level is judged to be zero / negligible have nothing special to do.
Family, friends, neighbors on a plane, medical staff … These surveys can potentially involve “several dozen” people and mobilize many professionals, even if it is variable, says Dr Coignard.
It all depends on how quickly a positive case is detected and how many people it has been in contact with.
According to Bruno Coignard, “the most complicated case” so far in France is that of a doctor contaminated by a Chinese patient, who then left for Asia (in Taiwan according to the Minister of Health Agnès Buzyn), where she been diagnosed.
It is the “contact tracing” set up around this person outside of France which made it possible to identify the doctor as one of his contacts, before the positive diagnosis was confirmed for him too.
Well established in developed countries, this device could be severely tested if the epidemic accelerates in places where health systems are fragile. A prospect that worries the WHO.
“If the epidemic spreads worldwide (…) the British system may find it difficult to check every suspicious case,” said Professor Martin Hibberd, of the London School of Hygiene & Tropical Medicine.
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