This is a cohort, non-health product, non-interventional biomedical research, multi-centric, to determine the seroprevalence of mpox infection in the population of people living with HIV and in PrEP users in Ile-de-France and in the province.

The target population is the population of people living with HIV (PLHIV) (n=18,500) and PrEP users (n=4930) followed up in Parisian infectious and tropical diseases departments (SMIT) of the Pitié-Salpêtrière, Tenon, Saint-Antoine, Bichat, Saint-Louis, Necker hospitals, the University Department of Infectious and Traveller Diseases of Hôpital Dron (Tourcoing), the 190 health center, and the Maison de santé du Chemin vert (Paris).

The principal objective is to determine the seroprevalence of Monkeypox infection in the population of PLHIV and PrEP users followed in the infectious and tropical disease departments in 9 centers.

In addition to the primary objective, there exist the following secondary objectives:

• To assess the level of anti-Mpox antibodies in PLHIV and PrEP users
• To assess the level of anti-Mpox antibodies in PLHIV and PrEP users with a previous confirmed diagnosis of Mpox or if they have been recently vaccinated
• Assess antibody levels in PLHIV in relation to CD4 cell count and HIV viral load
• Study antibody kinetics and persistence over time (D0 (between November 1, 2021 and April 30, 2022), M6, M12)
• Study the Mpox seroconversion rate over time
• Determine the neutralizing activity of anti-Mpox antibodies in individuals with positive anti-Mpox ELISA serology.
• Describe the natural history of the disease, the different forms of the disease, their clinical characterization
• Describe sexual behavior and the impact of this health crisis on different aspects of their lives using a self-administered questionnaire
• To determine the prevalence of asymptomatic infections
• Proportion of participants with positive Mpox serology without PCR confirmed diagnosis
• History of childhood or recent smallpox vaccination

During the patient's follow-up consultation, after information and in the absence of an expression of no objection, inclusion will consist of recovering a blood sample taken between November 2021 and April 2022 during the HIV infection assessment or PrEP follow-up (no additional sample) and possibly the blood sample taken at M6 and/or M12 if this follow-up consultation has already taken place.

An online self-questionnaire will also be proposed to the patient (male only). It will be constructed from questions already validated in other surveys (Rapport au Sexe, Prévenir, Parcours).

A check on the appearance or persistence of antibodies will be carried out at M6 +/- 8 weeks and/or M12 +/- 8 weeks on tube bottoms of samples always taken as part of the HIV infection assessment or PrEP follow-up.

Inclusion Criteria:

• Age ≥ 18 years
• People Living with HIV or PrEP users with a blood test within 6 months before the start of the epidemic (i.e. between 1/11/2021 and 30/04/2022, D0) and with a blood test scheduled at M6 and/or at M12 of this collection depending on the care, in the centers participating in the study
• Having been informed about the study and not having expressed his opposition
• Affiliated to a social security system or entitled person, AME beneficiary

Exclusion Criteria:

• Refusal of participation by the patient
• Under legal protection (guardianship/guardianship)
• Not able to understand the information and/or express opposition and/or not speaking French

The target population is the population of PLHIV (n=18,500) and PrEP users (n=4930) followed up in the infectious and tropical diseases departments (SMIT) in 9 centers in Ile de France and province.