<span style="color: #222222;">The second-largest Ebola outbreak in history has spread to a major city in eastern Congo. </span><br />'' <br />'' <span style="color: #222222;">Health experts worry whether the stock of an experimental vaccine will stand up to the demands of an epidemic with no end in sight. </span><br />'' <br />'' <span style="color: #222222;">Butembo, with more than one million residents, is now reporting cases of the deadly hemorrhagic fever. </span><br />'' <br />'' <span style="color: #222222;">This complicates Ebola containment work already challenged by rebel attacks elsewhere that have made tracking the virus almost impossible in some isolated villages.</span><br />'' <br />'' <span style="color: #222222;">The outbreak declared in August is now second only to the devastating West Africa outbreak that killed more than 11,300 people a few years ago. </span><br />'' <br />'' <span style="color: #222222;">Congo's Health Ministry said, there are currently 471 Ebola cases, of which 423 are confirmed, including 225 confirmed deaths.</span><br />'' <br />'' <span style="color: #222222;">The Ebola virus is spread via bodily fluids of those infected, including the dead.</span><br />'' <br />''