Hepatitis A Outbreak in France and Europe - Update as of July 27, 2017

Published on 31 December 1969

Since February 2017, several European countries have seen a significant increase in the number of hepatitis A cases, particularly among men who have sex with men (MSM); three "epidemic" strains of the hepatitis A virus are primarily responsible for this. Cases linked to this outbreak have been reported in many European countries (Austria, Belgium, Denmark, Finland, France, Germany, Greece, Ireland, Italy, the Netherlands, Norway, Portugal, Slovenia, Spain, Sweden, and the United Kingdom).

The situation in France

Hepatitis A is monitored in France through mandatory reporting and by the National Reference Center (CNR).

Epidemiological data

From January 1 to June 30, 2017, 1,149 cases of hepatitis A were reported: 65 in January, 89 in February, 156 in March, 191 in April, 300 in May, and 348 in June. The number of acute hepatitis A cases reported during the first 6 months of 2017 is already higher than the total number of cases reported in 2016 (693 cases).

This outbreak primarily affects men, who account for 914 (79%) of the 1,149 cases reported in 2017 (Figure 1).

Sexual orientation is not included in the information collected as part of the mandatory reporting system. However, clusters of cases among MSM are suggested when an increase in the male-to-female sex ratio is observed among reported cases and none of the classic risk factors are present (other cases or children in the household, work in a high-risk setting, travel outside mainland France, or consumption of seafood), or when sexual orientation is documented during investigations. The analysis of the male-to-female sex ratio presented below focused on cases aged 18 to 55 to avoid accounting for potential polyclonal reactions (a resurgence of hepatitis A-specific antibodies several years after a past infection), which are more common in those over 55.

The increase in the male-to-female sex ratio observed here (3.9 in 2017 vs. 1 in 2016) and the results of initial investigations into clusters of cases strongly suggest that the MSM population is the most affected by this epidemic, in France as in other European countries.

The most affected regions are Île-de-France (298), Hauts-de-France (226), followed by Auvergne-Rhône-Alpes (159), Provence-Alpes-Côte d’Azur (116), and Occitanie (84) (Map).

Starting in January 2017, the male-to-female ratio among the 910 cases aged 18 to 55 increased (Figure 2) and then decreased between May and June. By region, the sex ratio increased but to varying degrees. It is currently highest in the PACA region (14), followed by the Hauts-de-France and Île-de-France regions (9.1), and finally around 4 for the ARA and Nouvelle-Aquitaine regions.

Virological data

Between late 2016 and July 13, 2017, the CNR identified the presence in mainland France of three European "epidemic" strains circulating among MSM in many European countries. These strains are:

RIVM-HAV16090, known as "Nl Europride,"
VRD-521-2016, known as "UK travel to Spain,"
V16-25801, known as “Germany Munich/Berlin/Frankfurt.”

During this period, the CNR identified 475 samples containing one of these three strains; 431 (91%) of these samples were from men, with an average age of 37. The CNR’s genotyping results were as follows: 276 (58%) of the strains were of the VRD-521-2016 type, 190 (40%) of the RIVM-HAV16090 type, and 9 (2%) of the V16-25801 type.

In conclusion, the hepatitis A outbreak among men aged 18 to 55 now affects all metropolitan regions, albeit to varying degrees, with a significant contribution from transmission among MSM. Since May, there has been an increase in the number of women linked to clusters of cases observed in the general population, resulting in a decrease in the sex ratio. This trend—an increase in the number of women—will need to be confirmed in the coming months.