The US agency wants to prevent the virus from spreading to other countries.
United States federal agency, Centers for Disease Control and Prevention has issued a 'level-two' travel alert which requires visitors to show evidence of polio vaccination for traveling to polio-endemic countries.
The agency wants to prevent the virus from spreading to other countries.
According to the CDC, Asian countries that have reported polio outbreaks other than Pakistan are Afghanistan, Burma (Myanmar), Indonesia, China, Papua New Guinea, Philippines and Malaysia.
According to the travel alert, adults who have been vaccinated for polio in their childhood would need a single dose of polio vaccine before traveling to these polio-endemic nations. Such individuals would now need the adult booster dose - Inactivated Poliovirus Vaccine (IPV) booster - before traveling to these countries, the CDC recommends.
The World Health Organisation has asked visitors to show evidence of polio vaccination before leaving such polio-endemic countries.