Congo's health ministry says another Ebola case has been confirmed as the pace of new cases slows one month after the outbreak was officially declared.

There are now 38 confirmed cases of the virus, including 13 deaths, the said late Thursday. The newest confirmed case is in rural Iboko and is linked to a probable Ebola case who died May 20, the ministry said.

The outbreak which began in the remote northwest and was declared in the town of Bikoro has spread to the city of Mbandaka with a population of more than one million. That has complicated efforts to track contacts of those infected.

The World Health Organization, which was giving a briefing Friday on the outbreak, has vaccinated more than 1,000 people over the past two weeks, including who are at high risk. The virus spreads via bodily fluids of infected people, including the dead.

Health workers have visited more than 10,000 households in Mbandaka to raise awareness about Ebola, WHO said. Exit screening measures have been put in place to prevent the international spread of the virus, and WHO said it is supporting efforts by nine neighboring countries to scale up emergency response and preparedness.

Republic of Congo and Central African Republic are closest to the outbreak, but Congo is also bordered by Angola, Burundi, Rwanda, South Sudan, Tanzania, Uganda and Zambia.

WHO says the Ebola response will cost more than $15.5 million over nine months.

This is Congo's ninth Ebola outbreak since 1976, when the hemorrhagic fever was first identified.