Just last January, Pakistani officials announced that polio had been eliminated in their country. Now the paralyzing disease is back—and spreading through the Afghan refugee populations.

Less than two weeks ago, a Pakistani health official announced a special five-day anti-polio drive in Quetta, the capital of southwestern Baluchistan province. Officials there had found traces of the poliovirus in the city’s sewer system.

Syed Faisal Ahmed, coordinator for Emergency Operation Centre in Quetta, said that some 400,000 children under age five would be immunized against the deadly virus.

Last year, multiple anti-polio drives enabled Pakistan to announce that the virus had been nearly eliminated.

But polio remains present in Pakistan. This is mostly because the Taliban banned vaccinations, attacked medical staffers, and spread suspicions about the dangers of the vaccine. The Taliban has claimed responsibility for multiple shootings and bombings aimed at polio volunteers. Taliban leaders accuse health workers of using the vaccine to spread disease and to spy on them.

Over 1,300 teams are working to cover 39 local councils of the city amid tight security.

Pakistani officials say that without help from the international community, it will be difficult for Pakistan to care for some 1.5 million registered—and about as many undocumented—Afghan refugees living in Pakistan.