Taiwan has recorded its first locally-transmitted case of coronavirus since April. The island has had one of the most successful pandemic responses in the world, and the new infection ends a 255-day run without local transmission, underscoring the difficulties in controlling the virus even in areas where it has been largely stamped out.

According to a statement released by the island’s health ministry on Tuesday, a woman in her 30s was infected after having contact with a foreign pilot, who also tested positive for the virus, between December 8 and 12.

Taiwan has been coronavirus free since April 12, only recording imported cases. Passengers arriving on the island must go into quarantine and those who test positive are isolated and given treatment. Three such imported cases were also recorded Tuesday, bringing the total number of cases on Taiwan since the pandemic began to 770.