Challenges include low salaries for doctors, poor facilities, poor provision of equipment, and the frequent absence of essential drugs. Cuba has the highest doctor-to-population ratio in the world and has sent thousands of doctors to more than 40 countries around the world. According to the World Health Organization, Cuba is "known the world over for its ability to train excellent doctors and nurses who can then go out to help other countries in need". , there are around 50,000 Cuban-trained health care workers aiding 66 nations. Cuban physicians have played a leading role in combating the Ebola virus epidemic in West Africa.