Laboratory tests have identified that some of the pigs had porcine circovirus, a common disease that affects pigs but does not affect humans.

BBC: China pulls nearly 6,000 dead pigs from Shanghai river

The procine circovirus , which can be present in pigs but not affect humans, was detected in some tests of the dead animals, it said.

FORBES: Shanghai Dead Pig Count Hits 5,916, Government Paper Says

GlaxoSmithKline today participated in a U.S. Food and Drug Administration (FDA) advisory committee meeting convened to discuss recent findings of porcine circovirus (PCV) in rotavirus vaccines.

FORBES: Magazine Article

Authorities said one test detected a pig-borne disease in the river called porcine circovirus, but that doesn't normally affect humans, according to the U.S. Centers for Disease Control and Prevention.

WSJ: Floating, Dead Pigs Repulse Shanghai

Although the committee did not issue any formal recommendations, members widely acknowledged that the benefits of vaccinating infants worldwide against rotavirus disease clearly outweigh the theoretical risks associated with the presence of porcine circovirus type 1 (PCV-1) in the vaccines.

FORBES: Magazine Article