KINSHASA, Congo -- Thousands of doses of the experimental Ebola vaccine have arrived in Congo's capital amid the latest outbreak of the deadly disease, the health ministry said Wednesday. The 4,000 doses will be sent to the remote northwest where two confirmed Ebola cases, 20 probable ones and 20 suspected ones have been reported, spokeswoman Jessica Ilunga said. An additional 4,000 doses will be deployed in the coming days with more available if needed, the World Health Organization (WHO) said.

WHO has reported 23 deaths among the 42 cases as medical teams try to contain the hemorrhagic fever. Health experts have identified 500 contacts of the cases and they are now being traced, Ilunga said.

"The most important thing is to stop the spread of the disease, and to that end, what they have to do is track down everybody -- people who have contracted Ebola or even died from Ebola," CBS News foreign correspondent Debora Patta reports.

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WHO said it will use the "ring vaccination" method, which involves vaccinating voluntary contacts, contacts of those contacts and health care and other front-line workers. Health workers would be among the first to receive vaccinations, according to Ilunga.

Three nurses are among the suspected cases, and one is among the dead.

A health worker is sprayed with chlorine after visiting the isolation ward at Bikoro hospital, which received a new suspected Ebola case, in Bikoro, Democratic Republic of Congo May 12, 2018. STRINGER/REUTERS

The experimental vaccine has been shown to be highly effective against Ebola. It was tested in Guinea in 2015 during the outbreak that killed more than 11,300 people in West Africa from 2014 to 2016.

This is the ninth Ebola outbreak in Congo since 1976. While none has been connected to the one in West Africa, the experimental vaccine is thought to be effective against the Zaire strain of Ebola found in Congo.

CBS News' Patta said the fact that there is a vaccine marks a significant difference between the outbreak in West Africa that started in 2014 and the outbreak in the Congo today.

"It can't cure Ebola, but what it can do is stop the spread of the disease," she said.

Patta also reports that a crucial difference between the two outbreaks is the speed at which international agencies have responded.

"In 2014, you remember that the World Health Organization and other agencies were criticized for being 'staggeringly slow' to respond," Patta said. More than 11,000 people died before the outbreak was contained.

"This time, they've wasted no time," she said.

Patta reports that the epicenter of the disease is a small, remote town called Bikoro. Congo's health ministry announced the Ebola outbreak on May 8 after two cases were confirmed there. The Bikoro health zone is about 150 kilometers -- 93 miles -- from Mbandaka and 45 kilometers from Ikoko Impenge, where suspected cases have been reported.