The number of cases of avian influenza in the Netherlands is still rising but the disease remains confined to the central Gelderland province.

Several new cases are being reported each day, with the total number of farms with confirmed cases now standing at 97. The number of farms with suspected cases is now 37, agriculture ministry spokesman Benno Bruggink told Reuters.

“We don’t know really (when the number of cases will stop growing). Our epidemiologists are working on it, trying to find the logic of where it’s expanding,” Bruggink added.

The outbreak of the highly contagious disease is estimated to have cost the poultry sector in the Netherlands, which has around 100 million birds, more than €40m (US$42.6m) since the disease was discovered three weeks ago.