A pauci-symptomatic case of documented Hantavirus (Puumala) infection in a patient under anti-TNF treatment.

We describe the case of an 18-yr-old male under anti-TNF treatment for Crohn's disease for more than 8 months. He developed fever and biological inflammatory syndrome without absolutely no accompanying sign or symptom or paraclinical abnormality despite extensive work-up performed in the context of his immunocompromised state. Symptoms disappeared after 10 days and a diagnosis of Puumala infection was made retrospectively on a serological basis.