Government figures show half of the 241 confirmed cases of novel Coronavirus in Pakistan are in people who went on pilgrimages to Iran.
Pakistan shares a 960-kilometre border with Iran, with the main crossing point at Taftan in Balochistan province.
Hundreds of Pakistanis who returned home from a pilgrimage to Iran are stuck in filthy Coronavirus quarantine camps with limited medical care, and fear squalid conditions are helping spread the disease.
Current and former residents of Taftan camp on the border with Iran said the facility lacks running water or flushable toilets, with detainees only able to wash every few days.
Iran has been scrambling to contain COVID-19 since authorities announced the first two deaths last month.
Nearly 1,000 people have since died, making Iran the third-hardest-hit country after China and Italy.
The Taftan border has been closed since March 16, but thousands of Pakistan Shi’ite pilgrims who were visiting religious sites in Iran have been allowed to return subject to two weeks’ quarantine.
They are then also expected to undergo a further two weeks quarantine in their home towns.
Taftan was built years ago specifically as a resting station for returning pilgrims, but has been overwhelmed by the crush caused by the virus.
Videos circulating on social media show people sleeping on floors and in corridors of permanent structures, and packed into tents erected in a dirty courtyard.
No attempt has been made to separate sick pilgrims from the healthy.
