More than 20,000 people have been diagnosed with Ebola virus and more than 7,800 have died of it, according to the latest data from the World Health Organization. It’s a new milestone in the ever-worsening Ebola epidemic in Sierra Leone, Liberia and Guinea, and it shows Sierra Leone has more cases than any other country.

Earlier Monday, Liberian authorities reported dozens of new Ebola cases along its border with Sierra Leone.

But the updated tally also show that belated international efforts to fight the virus are having at least some effect. In September, the WHO’s worst-case scenario projected 20,000 cases by mid-November. WHO now says the spread of the virus is unlikely to be under control before the middle of next year.

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-- Maggie Fox