Measles: resurgence of cases last year… and fears for the Olympics

Measles: resurgence of cases last year… and fears for the Olympics

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“We must not declare victory too quickly! » Asked last year about the virtual absence of circulation of measles in 2022 in France, pediatrician Christèle Gras-Le Guen remained cautious. Rightly so: the report for the year 2023, published this Wednesday by Public Health France and which Le Parisien was able to consult in preview, testifies of a resurgence of this disease which mainly affects children and adolescents. But as the Olympic Games approach, population flows raise fears of several imports of the virus into France. We take stock.

A still very limited number of cases

117 confirmed cases of measles, spread over sixteen departments, were reported last year. This toll is eight times higher than that for 2022 but we remain very far from those for 2020 and, especially, 2019 (respectively 240 and 2,636 cases). The virus had in fact circulated very little over the past three years, simply causing “a few isolated sporadic cases”. The strong epidemic wave of 2019 and the very high vaccination coverage of infants have undoubtedly made it possible to temporarily achieve a form of collective immunity.

In this context, any comparison with 2022 should be interpreted with caution (in December, the World Organization mentioned a number of cases multiplied by 45 in the Europe zone!). 27 of these 117 patients in France were hospitalized, but none died.

Many imports from abroad

The vast majority of measles patients last year are linked to a probable importation of the virus from abroad. These may be “imported” cases, that is to say infected elsewhere than in France, or – most often – contaminated on French soil by a person returning from abroad.

This situation “confirms the resumption of the circulation of measles in the world”, indicates Public Health France. And the agency warns that “the risk of importation into France is increasing”, with the approach of the Paris Olympic Games which will attract a large number of people. “The international situation is marked by an epidemic resumption, linked to the drop in vaccination coverage observed in most countries,” warns Laura Zanetti, deputy head of the Respiratory Infections and Vaccination Unit at Public Health France.

“Pockets of circulation” highlighted

Half of these 117 patients were children under 12 years old, the others were older. A single outbreak in a college has 64 cases, including 50 adolescents. His “patient zero” is an unvaccinated child, returning from a trip to Indonesia. Other smaller “clusters” have been reported in primary schools, hospitals or within families.

Public Health France points to “the existence of pockets of the population still receptive to the measles virus, in particular among adolescents and young adults as well as among travelers going to endemic areas”. As a result, “if the virus is introduced into French territory, this could cause epidemic outbreaks,” indicates Laura Zanetti.

Vaccination, “the only effective protection measure”

As there is no specific treatment for measles, “vaccination is the only effective protection measure”, points out Public Health France. Roughly speaking, half of the measles cases last year were vaccinated (most often with two doses) and the other half were not. “We had, quite unusually, a high number of correctly vaccinated cases, particularly in college. Many of these adolescents had been immunized before they were nine months old. However, we now know that too early vaccination provides less immunity over time,” says Laura Zanetti. From now on, the first dose is recommended at twelve months.

More generally, since a vaccine is never 100% effective, it is normal and expected that a proportion of patients are not immunized since almost the entire population is. In France, we are approaching vaccination coverage of 95%, “an objective set to interrupt the circulation of the measles virus”. Since 2018, vaccination against this disease has been mandatory. For adolescents and adults who have not received their two doses, a “catch-up” is recommended.

The 2024 toll is expected to rise further compared to 2023. In Rhône and Drôme alone, the Regional Health Agency is already reporting 59 cases of measles spread over two outbreaks between January and March. “The dynamic is accelerating, both in terms of outbreaks and the number of cases,” warns Laura Zanetti, who calls on “anyone to check that they have received their two doses”.

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