More than 5.8 million birds have been slaughtered in the last year to contain the worst outbreak of bird flu in nearly 20 years.

The Netherlands Food and Consumer Product Safety Authority (NVWA) has found the H5N1 variant of bird flu on 96 poultry farms since it was first detected in Zeewolde on October 26 last year.

In Heythuysen, Limburg, 300,000 birds will have to be destroyed in the biggest outbreak at a single location so far, the agriculture ministry said on Thursday.

An 10-kilometre exclusion zone has been set up around the infected poultry farm, banning 128 other farmers in the area from distributing manure, eggs and other animal products.

Altogether 4.7 million birds have been killed on infected farms, while another 1.1 million have been exterminated to try to prevent the disease spreading further. The real number is almost certainly higher as the NVWA does not monitor smallholdings with fewer than 50 animals.

The H5N1 strain has been present in Europe since 2005 and is spread by wild birds. Walkers and beachgoers have been warned to stay away from dead birds in case they are infected.

The last comparable outbreak of bird flu in the Netherlands was in 2003, when 30 million creatures at 255 sites were killed.

The European Centre for Disease Prevention says the current outbreak is the worst in the continent’s history, spanning 37 countries from Norway to Ukraine.