The United Nations is warning the Ebola outbreak in West Africa continues to spread unabated. In a new update, the World Health Organization says nearly 3,900 people have been killed out of the more than 8,000 confirmed to have contracted the disease. The U.N. special envoy on Ebola, David Nabarro, said the outbreak is increasing exponentially.

Dr. David Nabarro: “I want to stress that this outbreak is increasing in size in an exponential way, which means if I draw it like that, the curve is going up. Curve is going up like that. And to get on top of that kind of epidemic curve requires an absolutely massive response. I’ve asked for a 20-fold increase in response compared with what we had at the end of August.”