JOHANNESBURG (AP) — International aid organization Doctors Without Borders said that 16 of its staff members have been infected with Ebola and nine of them have died.

Speaking at a press conference in Johannesburg Tuesday, the head of Doctors Without Borders in South Africa Sharon Ekambaram said medical workers have received inadequate assistance from the international community. She said that while many pledges had been made publicly they have not improved the situation in the affected countries.

Juli Switala, a doctor working for the international aid organization who just returned from Sierra Leone, said the number of those who have died from Ebola is probably an underestimate because many families hide their sick and dying loved ones. More than 4,000 people have died from Ebola so far, according to the World Health Organization.