(CNN) Nearly 100 children have died since the Ebola outbreak in the Democratic Republic of Congo started last year -- and the crisis is gathering pace, with the number of new cases doubling last month, according to charity Save the Children.

A total of 97 children have died from the viral illness since the outbreak began in August, 65 of whom were younger than 5 years old, the group said.

And the number of new cases spiked in January, from around 20 a week to more than 40, according to the charity. In the last three weeks of January alone, there were 120 new cases overall.

Ebola -- which causes fever, severe headache and in some cases hemorrhaging -- kills about half of those infected on average, though the latest outbreak has a fatality rate of around 60%.

The current outbreak in Congo is the second-deadliest and second-largest in history, topped only by one in West Africa in 2014, when the disease killed more than 11,000 people, according to the World Health Organization.

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