How did travelers contribute to polio outbreaks in Tajikistan and China in 2010 and 2011?

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Polio vaccine — polio A health care worker giving a polio vaccine to a child in Katsina state, Nigeria, 2014.

Travelers from polio-endemic regions frequently exported the virus to countries that had previously eliminated the disease, leading to significant outbreaks.

In April 2010, an outbreak occurred in Tajikistan, which had been polio-free for over a decade. The outbreak was caused by a strain of PV1 that was genetically very closely related to a strain circulating in Uttar Pradesh, India.1

Similarly, in August 2011, China reported its first cases of polio since 1999. The virus identified in these children was genetically similar to poliovirus circulating in Pakistan, which was experiencing a surge in cases at that time.1

These incidents highlight the ongoing challenge of international transmission, as large-scale population movements—such as those associated with pilgrimages to Mecca—can facilitate the spread of the virus from endemic areas to polio-free regions.1