A case of fatal encephalitis caused by a pigeon-borne virus

From the outbreak of Andes hantavirus aboard the MV Hondius cruise ship to the ongoing Ebola epidemic in the Democratic Republic of the Congo, recent news events have provided a timely reminder of the risk represented by viruses circulating in animals that can be transmitted to humans. 
The outbreaks also demonstrate the importance of adopting a One Health approach. As we witness the impacts of climate change and environmental transitions, it is clear that human, animal and environmental health are more closely interlinked than ever. Monitoring zoonoses, diseases caused by infectious agents that can spread from animals to humans, is therefore crucial.
 

Newcastle disease virus, prevalent in birds

The avian influenza virus, currently in active circulation in birds, has also given rise to isolated cases in humans in recent months and remains under close surveillance.
Another virus, less well known to the public, is the Newcastle disease virus, which is widespread in birds. It is a notifiable disease because of the virulence of some strains and the contagious nature of the virus in birds. If a case is confirmed on a poultry farm, culling orders are issued.
A variant of the virus, pigeon paramyxovirus type 1 (PPMV-1), circulates widely in pigeon populations worldwide. It can be transmitted to humans, but severe forms of infection are extremely rare. Until recently, only a few serious cases had been documented anywhere in the world; these were fatal cases associated with respiratory syndromes and two deaths from encephalitis.

A first death in France and the first in a non-immunocompromised individual

A collaborative study involving the Institut Pasteur, Paris Public Hospital Network (AP-HP), Necker-Enfants Malades Hospital and ANSES recently reported a third human death from encephalitis caused by PPMV-1. This is the first death in France, and the first in an individual not believed to be immunocompromised. "The infectious agent was only identified after the patient's death, using next-generation metagenomic sequencing on port-mortem tissues," explains Nolwenn Dheilly, Head of the Pathogen Discovery laboratory. The subsequent epidemiological investigation revealed that the individual had probably contracted PPMV-1 at a shamanism workshop, where he is thought to have come into contact with bird droppings.

Improving diagnosis for severe cases, which remain very rare

Despite the description of this third death, it is important to point out that severe forms of the disease are extremely uncommon. In the vast majority of cases, the virus causes mild conjunctivitis in humans, which resolves without treatment. Severe cases could be more easily diagnosed in future. "Standard PCR tests on cerebrospinal fluid do not detect the virus. But PPMV-1 was found in the lymph nodes, so a minimally invasive lymph node puncture could be used to detect the virus at an earlier stage," continues Nolwenn Dheilly.
The study emphasizes the importance of epidemiological surveillance to identify viruses that are potentially pathogenic for humans, and encourages clinicians to consider PPMV-1 as a possible cause of encephalitis of unknown origin.

One Health Investigation into Fatal Encephalitis Caused by Pigeon Paramyxovirus Type 1, France, Emerging infectious diseases, mai 2026

Nicolas Veyrenche1,2, Susana Boluda3,9, Philippe Pérot4,9, Isabelle Malissin5, Marianne Leruez-Ville1,2, Anne Jamet1, Agnès Ferroni1, Béatrice Regnault4, Maud Salmona6,7, Linda Feghoul5, Laurine Robert-Capraro4, Aurélie Leroux8, Béatrice Grasland8, Eric Niqueux8, François-Xavier Briand8, Isabelle Plu3, Danielle Seilhean3,10, Bruno Megarbane5,10, Jacques Fourgeaud1,2,10, Nolwenn M Dheilly4,10

1Hôpital Necker-Enfants malades, Paris, France

2Université Paris Cité, FETUS, Paris

3APHP-Hôpital de la Pitié-Salpêtrière, Sorbonne Université, Paris

4Institut Pasteur, Université de Paris, Paris

5Lariboisière Hospital, Paris Cité University, INSERM UMRS-1144, Paris

6Saint-Louis Hospital, APHP, Paris

7Biology and Pathogenesis of Viral Infection team, INSERM UMR 1342, Saint Louis Research Institute, Université Paris-Cité, Paris

8Anses, Ploufragan-Plouzané-Niort Laboratory, Ploufragan, France

9These authors contributed equally to this article

10These senior authors contributed equally to this article.