The Telangana government on Tuesday declared a “global emergency” after an active strain of poliovirus (P2 strain) was found in a water sample collected from a drain in Hyderabad. Telangana health officials told that the virus found was a vaccine-derived strain of the virus. In a mass vaccination drive, more than three lakh children in the city and Ranga Reddy district will be inoculated Wednesday onwards as a “preventive measure”. Two lakh vaccines were airlifted from Geneva immediately after the virus was detected, The Times of India reported.

“The government has decided to conduct a special campaign against polio in Hyderabad and parts of Ranga Reddy from June 20 to June 26,” the principal secretary of health, Rajeshwar Tiwari, said, adding that the vaccine-derived polio strain was previously detected in Bihar, Gujarat, Uttar Pradesh and Delhi, as well.

The virus was found in a sample taken from the Amberpet sewerage treatment plant on May 17. It was part of a routine surveillance in which 30 samples were collected from various parts of Hyderabad.

The chief programme officer of Telangana’s National Health Mission, Dr G Srinivasa Rao, said they will follow “WHO-set standards” during immunisation programmes. Children between the ages of six weeks to three years will be given additional doses of the injectable polio vaccine, Rao added. Booths will be set up in areas being covered in this campaign, which does not include door-to-door services.

Since January 2014, India has reported at least four occurrences of vaccine-derived polio but here have been no cases of infection from the wild polio virus since January 2012. India was declared polio-free by the World Health Organisation in 2014. However, the vaccine-derived strain must be contained because neighbouring and West Asian countries, which are well connected with Hyderabad, continue to see new cases.