Genzyme’s stock took a hit yesterday on news that it has temporarily shut down its manufacturing facility in Boston after a bioreactor was contaminated with a virus, affecting production of its enzyme replacement drugs Cerezyme and Fabrazyme.

Shares in the group closed down more than 5% after the firm announced that the viral strain Vesivirus 2117, which is considered not to be harmful to humans, was detected in one of its six bioreactors at the facility, forcing the plant’s closure until the end of July.

The company has warned that current batches of Cerezyme (imiglucerase), a treatment for Gaucher disease, and Fabrazyme (agalsidase beta), which is indicated for Fabry disease, “are not sufficient to meet projected global demand”, and while the exact effect on the former remains undetermined it expects supply constraints for Fabrazyme for a limited period in September.

While Genzyme insists any impact from the plant closure will be temporary, this is not the first time the virus has been detected at the facility as it follows two prior cases in 2008, and the company said it is now “adding steps to increase the robustness of its raw materials screening and viral removal processes”.