ANNAPOLIS, Md. (AP) – Agriculture officials said Friday they plan to lift restrictions on nearly 2,000 poultry farms in Delaware and Maryland after a month without any reports of avian influenza.

The virus, also known as bird flu, has forced the killing of more than 400,000 birds since February. The cases were from the H7 strain, the most common form of bird flu but one that is not harmful to humans.

Starting Monday, farmers will be allowed to spread manure made from chicken litter and receive new baby birds from poultry companies. The virus spreads easily on manure and feathers.

The type of bird flu that has struck Delaware and Maryland poultry farms can be no worse than the chicken equivalent of the common cold. If left to spread, however, the disease can mutate into highly pathogenic varieties that can kill entire flocks in a day.

A different avian influenza strain has been blamed for the deaths of more than 20 people in Vietnam and Thailand.

Agriculture workers in Delaware and on Maryland’s Eastern Shore launched an unprecedented avian flu testing program after the virus was discovered in Delaware in February.

Until April 13, workers will continue to test flocks for the virus before they leave the farms for processing, said Maryland Department of Agriculture spokeswoman Sue DuPont.

AP-ES-04-02-04 1838EST