Influenza in seals

There are four types of influenza in total. Types A, B and C cause flu in humans. Influenza types A and B can occur in marine mammals, such as in seals. Influenza can cause a huge wave of disease in wild seals.

Influenza is not clearly visible by one specific complaint or change in appearance. Seals can have several complaints at the same time. The characteristics of influenza B are unknown. Possible features of influenza A are:

• Weakness
• Bad coordination
• Short of breath
• Swollen neck
• White or bloody runny nose
• Pneumonia

The virus droplets are spread by, among other things, coughing and sneezing, and are then inhaled again. Influenza is extremely contagious. Not only for seals, but also for humans. That is why it is very important to protect both the seals and ourselves if someone is carrying the virus.

Common and grey seals can be sick with influenza. It is shown that mainly common seals suffer from the influenza virus. In several major outbreaks of the virus, mainly common seals died. The last outbreak of influenza was in 2014, when thousands of common seals washed up dead on the coasts of the Netherlands, Germany, Denmark and Sweden (1).

Zeehonden kunnen ook influenza krijgen van vogels. In 2014 was het vogelgriepvirus (H10N7) de veroorzaker van grote sterfte onder gewone zeehonden (2). Waarschijnlijk liepen zeehonden het virus op door direct of indirect contact met wilde vogels of hun uitwerpselen.

In June 2022, researchers found the avian flu virus in three seals in Germany, but it hasn't sparked a massive outbreak. The fact that the virus is transferred from a bird to a marine mammal means that there is a chance that humans can also be infected.

Op 16 december 2025 werd op Vlieland een jonge gewone zeehond dood aangetroffen. Het dier is naar ons centrum gebracht voor onderzoek, waar bleek dat het niet – zoals verwacht bij zeehonden van deze leeftijd – stierf aan een longworminfectie. Omdat het dier verder ook in goede conditie was, is er melding gemaakt bij het NVWA. Uit de eerder genomen monsters en een onderzoek naar hersenweefsel door de NWVA bleek dat het dier besmet was met vogelgriep. Of dit de doodsoorzaak was, blijft echter onzeker.

It is not possible to cure influenza. There is no medicine for this virus. We can only try to reduce the symptoms and wait until the seal gets better.