Status: Wild poliovirus type 1 (WPV1) detected in environmental sample

On 9 May 2019, WHO received notification through the Global Polio Laboratory Network (GPLN) of the detection of wild poliovirus type 1 (WPV1) from an environmental sample in Iran, Seestan-Baluchistan Province.  The virus was detected in an environmental sample only – no associated cases of paralysis have been detected.

The affected province borders both Baluchistan, Pakistan, and part of Southern Region, Afghanistan and genetic sequencing has confirmed that the isolated virus is linked to WPV1 circulating in Karachi, Pakistan.

An immediate risk assessment suggests that this event has limited public health implications, given Iran’s very high levels of routine immunization coverage and strong disease surveillance.  At the same time, this event further underlines the risk of renewed international spread of WPV1 from Pakistan and Afghanistan.

Polio this week in Iran

  • No new WPV1-positive environmental samples were reported this week.  In total, three WPV1-positive environmental samples were reported in 2019, all from Sistan and Balochistan province.  The isolated viruses were detected in environmental samples only, and genetic sequencing confirms they are linked to WPV1 circulating in Karachi, Pakistan.
  • Read our Iran country page for more information.

WHO risk assessment

WHO assesses the risk of international spread of this strain of WPV1 from Iran to be low.  WHO assesses the risk of further international spread from Pakistan and/or Afghanistan to be high.

WHO advice

It is important that all countries, in particular those with frequent travel and contacts with polio-affected countries and areas, strengthen surveillance for AFP cases in order to rapidly detect any new virus importation and to facilitate a rapid response. Countries, territories and areas should also maintain uniformly high routine immunization coverage at the district level to minimize the consequences of any new virus introduction.