BUNIA, Congo — Ebola has killed more than 1,700 people in eastern Congo in what has become the fastest-growing outbreak of the disease, according to data — spreading faster than health officials can track and with patient zero still unidentified. “Contact tracing is not working,” said Kaseya, “we don’t like the trajectory of this outbreak, and it’s already the second largest outbreak (ever) in the world.” Delays in contact tracing, difficulties accessing affected areas, mistrust from communities, and violence by armed groups and some residents have hampered the response, the Africa CDC has said. The WHO says more than 100 health care workers have been infected since the beginning of the outbreak. AdvertisementThe response is also hampered by a funding gap, attacks on health centers, an ongoing conflict in eastern Congo and mistrust among local communities.