KINSHASA, Congo -- There are now 14 confirmed Ebola cases in Congo's latest outbreak as health officials rush to contain the often deadly virus in a city of more than 1 million. Vast, impoverished Democratic Republic of Congo has contained several past Ebola outbreaks but the spread of the hemorrhagic fever to an urban area poses a major challenge.

The city of Mbandaka, which has one confirmed Ebola case, is an hour's flight from the capital, Kinshasa, and is located on the Congo River, a busy travel corridor.

The World Health Organization was holding an emergency meeting on Friday. It now calls the risk to the public in Congo "very high" and the regional risk "high." It says no international travel restrictions are in place. The Republic of Congo and Central African Republic are nearby.

"This is a major, major game-changer in the outbreak," Dr. Peter Salama, WHO's emergency response chief, warned on Thursday after the first urban case was announced. "Urban Ebola can result in an exponential increase in cases in a way that rural Ebola struggles to do."

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The outbreak tests the new experimental Ebola vaccine, which proved highly effective in the West Africa outbreak a few years ago. 4,000 doses have arrived in Congo, with thousands more to follow, CBS News' Jonathan Lapook reports. The plan is to immunize the more than 500 contacts of infected people in an attempt to stop the virus from spreading. One challenge will be keeping the vaccine cold in a region with poor infrastructure and patchy electricity.

Just one Ebola death in this current outbreak has been confirmed so far. Congo's health ministry late Thursday said the total number of cases is 45, including 10 suspected and 21 probable ones.

The health ministry said two new deaths have been tied to the cases, including one in a suburb of Mbandaka. The other was in Bikoro, the rural area where the outbreak was announced last week. It is about 93 miles from Mbandaka.

Until now, the outbreak had been confined to remote rural areas, where Ebola, which is spread via contact with bodily fluids of those infected, travels more slowly.

Doctors Without Borders said 514 people believed to have been in contact with infected people were being monitored. WHO said it was deploying about 30 more experts to Mbandaka.

This is the ninth Ebola outbreak in Congo since 1976, when the disease was first identified. The virus is initially transmitted to people from wild animals, including bats and monkeys.

There is no specific treatment for Ebola. Symptoms include fever, vomiting, diarrhea, muscle pain and at times internal and external bleeding. The virus can be fatal in up to 90 percent of cases, depending on the strain.