Congo's Ebola death toll passes 5,000 as Nigeria rules out two suspected cases

The outbreak is caused by Bundibugyo virus, a rare Ebola species with no approved vaccine or treatment, AP and Reuters reported. The CDC says it is now the second-largest Ebola outbreak on record, with cases also confirmed in Kenya, Nigeria and Uganda.

In Nigeria, the Nigeria Centre for Disease Control and Prevention said on Sunday that samples from two suspected cases in the northeast tested negative after two rounds of testing, Reuters reported. The country's only confirmed case remains a Swiss woman who had traveled to Uganda.

Why it matters: The CDC says the risk to the American public remains low. Under a CDC requirement that takes effect after 11:59 p.m. Eastern on November 3, every passenger boarding an international flight to the United States must sign a statement that they have not been present in Congo.