Health officials have begun rolling out mass vaccines to combat an Ebola 'crisis' that has sparked pandemic fears.

The World Health Organization (WHO) said Sunday that vaccination in the Kasai province of the Democratic Republic of the Congo (DRC) is being offered to people exposed to the Ebola virus and front-line health workers.

The limited number of vaccines is being rolled out as cases of Ebola more than doubled in the last week, from 28 to 68.

The outbreak, which was officially declared earlier this month, has left at least 16 dead, including four healthcare workers.

An initial 400 doses of the Ervebo vaccine, an FDA-approved shot administered only during outbreaks, have been dispatched in Bulape, a current Ebola hotspot in the Kasai province.

The rest are set to be delivered in the coming days, the WHO said.

The WHO's International Coordinating Group on Vaccine Provision has approved an additional 45,000 vaccines, boosting the DRC's existing stockpile of 2,000.

Treatment courses of the monoclonal antibody therapy drug Mab114 have also been sent to treatment centers in Bulape. Also known by its brand name Ebanga, the drug targets glycoprotein, the protein that allows the Ebola virus to infect cells, and prevents it from attaching to the host cells and replicating.

A healthcare worker is pictured putting on protective equipment before checking on patients during the 2018 Ebola outbreak in the Democratic Republic of the Congo (DRC)

Pictured is a healthcare worker filling a syringe with an Ebola vaccine in the DRC in 2019. Vaccines are generally not available to the public and are only used during an outbreak

Your browser does not support iframes.

The WHO said in a statement: 'The Ervebo vaccine is safe and protects against the Zaire ebolavirus species, which has been confirmed as the cause of the ongoing outbreak.'

Ebola's presence in DRC dates back to 1976, and the latest outbreak is the 16th in the country and the seventh in Kasai province.

Read More Passengers on flight from South Korea to New York quarantined over 'highly infectious' contagion

Previous outbreaks in 2018 and 2020 in eastern Congo killed more than 1,000 people each.

The largest Ebola outbreak occurred in 2014 to 2016 in West Africa when more than 28,600 cases were reported.

Francois Mingambengele, administrator of the Mweka territory, which includes Bulape, told Reuters earlier this month: 'It's a crisis, and cases are multiplying.'

Ebola spreads through contact with the blood or body fluids of an infected person, as well as contact with contaminated objects or infected animals such as bats or primates.

Symptoms include fever, headache, muscle pain and weakness, diarrhea, vomiting, abdominal pain and unexplained bleeding or bruising.

Ebola can cause serious disease and has a mortality rate as high as 90 percent without treatment.

The current outbreak is caused by the Zaire ebolavirus species, which kills 36 to 90 percent of patients. It is the most common virulent ebolavirus species and is thought to be transmitted from animal reservoirs, likely bats, to humans.

Residents in some areas have been placed in confinement to prevent the spread. Local officials have also erected multiple checkpoints along the border to prevent people from traveling in or out of the Kasai area.

A healthcare worker in the DRC is pictured during a 2018 Ebola outbreak

Ebanga and Inmazeb, another monoclonal antibody, are the two FDA-approved treatments for Ebola.

The first confirmed case in the DRC's current outbreak, according to the WHO, was a pregnant woman who went to Bulape General Reference Hospital on August 20 with a high fever, bloody stool, excessive bleeding and weakness.

She died five days later from organ failure, and testing on September 4 confirmed Ebola.

Earlier this year, another outbreak was declared in Uganda, with 12 confirmed cases and two probable, as well as four deaths. The outbreak was declared over in April.

The outbreak was declared over the Sudan Virus, a rare virus that causes a severe form of Ebola hemorrhagic fever.

Along with the typical Ebola symptoms, it also causes bleeding from the eyes, nose, gums and other body parts, organ failure and death.

New York officials suspected two patients at a Manhattan urgent care may have had Ebola earlier this year because the patients had recently traveled from Uganda where there was an outbreak of the disease at the time

In February of this year, two suspected Ebola cases were detected in the US. Patients were transported from a New York City urgent care to a hospital after they exhibited symptoms of the disease.

Officials suspected they could have had Ebola infections because the patients had recently traveled from Uganda, where an outbreak was ongoing at the time.

It was later confirmed that they did not have Ebola, but it was not revealed what illness they were suffering from.

The first person to have a confirmed Ebola infection in the US was a man from Liberia in 2014. He had traveled to the US, where he began experiencing Ebola-like symptoms.

After tests confirmed the illness on September 30, 2014, he became the first US patient to have the disease. He died a week later.

Mass vaccinations begin as panic over Ebola pandemic 'crisis' spreads