Just days before Shanghai is inundated with travelers for its world exposition, China has lifted a two-decade ban on those who carry the HIV virus or others with sexually transmitted diseases, the New York Times reports, also lifting a travel ban on those with leprosy. The changes were approved on April 19 and came into effect on April 24, amending a 1986 law governing quarantines and a 1989 law that regulates entry by foreigners. Although the ban on HIV-positive travelers has been lifted temporarily for other major events, this change is believed to be permanent, and was in the works since the 2008 Beijing Olympics. The U.S. dropped a ban on HIV-positive visitors, in effect for 22 years, in January.