While the winter epidemic of classic flu is running out of steam, virologists have their eyes fixed on a little-known virus which has just reached a crucial stage: transmission between humans.
Until now confined to stables and herds of cattle, a new flu has reached a stage that worries the scientific community. If it does not yet cause waves of hospitalizations like influenza A, at the start of the year it became the number 1 “point of vigilance” for virologists. The alert was given at the end of January 2026 by researchers from the Emerging Pathogens Institute: a strain isolated in China during the winter of 2025-2026 revealed contamination between humans (around ten cases grouped within families where only one member worked in contact with cows). It is no longer just animals that infect humans: for the first time, the virus has been traced passing from one individual to another within family groups, confirming that the virus has crossed the human-to-human barrier.
The concern is reinforced by a fragile immune context. Lhe classic seasonal flu dominated this year by the K variant of the H3N2 virus (against which the current vaccine has shown limited effectiveness) has hit the organisms hard. Experts fear that this flu – called influenza D – will take advantage of this drop in overall defense to take hold. In the United States, recent serological tests already show that 97% of workers in contact with cattle have antibodies, proof of much wider circulation than imagined. In the general population, no massive epidemic outbreak has been declared to date, but the virus is now classified by the WHO as a “pathogen with pandemic potential” to be closely monitored.
In 2026, influenza D is described as a “subclinical” infection. This means that if you catch it, you are likely to have no symptoms or very mild signs such as mild throat irritation, temporary fatigue and mild cold symptoms. The danger is not its current virulence, but its capacity to mutate.
Experts fear that for every case identified in the laboratory, there could be hundreds more in the general population that go unnoticed (mistaken for a common cold). “If this virus develops the ability to spread easily from person to person, it could cause epidemics or even pandemics, as most people will not be immune“, declares John Lednicky, co-author of the study and research professor. China and the United States are the two areas of maximum surveillance due to the density of industrial farms. In France, the Directorate General of Health issued enhanced vigilance bulletins at the beginning of 2026. In March 2026, although the classic flu epidemic ended at the end of February, surveillance of zoonoses remains at a “high” level. We are particularly monitoring farms cattle in Brittany and the Great West.
The 2026 influenza vaccine does not protect against type D. Prevention is therefore purely behavioral. Professionals must strictly wear a mask and gloves in the presence of livestock. The general public must avoid direct and unprotected contact (stroking, visits to educational farms) with farm animals in the event of a local epizootic. Hand washing remains the best barrier, the D virus being sensitive to hydroalcoholic solutions. For information, the name “flu D” simply follows the alphabetical order of the findings of the Influenza virus families. Its genetic characteristics are different enough from types A, B and C to constitute a group in its own right. Its structure is closer to type C, but it primarily attacks cattle.
