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
- One wild poliovirus type 1 (WPV1)-positive environmental sample was reported in the past week, from Sistan and Balochistan province, collected on 20 May 2019.
- In total, three WPV1-positive environmental samples have been reported in 2019, all from Sistan and Balochistan province. The isolated viruses have been detected in environmental samples only, and genetic sequencing confirms they are linked to WPV1 circulating in Karachi, Pakistan.
- The Ministry of Health and local health authorities are undertaking a detailed investigation and the partners of the Global Polio Eradication Initiative (GPEI) are on standby to provide support as required. 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. However, this event further underlines the risk of international spread of WPV1 from Pakistan/Afghanistan.
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.
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.
International Health Regulations
Countries affected by poliovirus transmission are subject to International Health Regulations Temporary Recommendations that request them to declare a case of polio as a national public health emergency and consideration vaccination of all international travellers, as per temporary recommendations issued as of May 2019.
WHO’s International Travel and Health recommends that all travellers to polio-affected areas be fully vaccinated against polio. Residents (and visitors for more than 4 weeks) from infected areas should receive an additional dose of OPV or inactivated polio vaccine (IPV) within 4 weeks to 12 months of travel.