According to the World Health Organization, the biggest health threats in 2019 include HIV, Ebola, and climate change.
There's also a surprising new threat on this year's list: vaccine hesitancy.
The news comes amid new outbreaks of measles in the US, including 170 cases reported since September in New York alone.
The WHO says the disease rose by 30 percent globally between 2016 and 2017.
There are many reasons people might not get vaccinated, but vaccine hesitancy is defined as reluctance or refusal to vaccinate despite the availability of vaccines.
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