The Ebola outbreak in West Africa is spreading faster than efforts to control it, World Health Organization (WHO) head, Margaret Chan, has said.
She told a summit of regional leaders that failure to contain Ebola could be “catastrophic” in terms of lives lost.
But she said the virus, which has claimed 729 lives in four West African countries since February, could be stopped if well managed.
Ebola kills up to 90% of those infected.
It spreads by contact with infected blood, bodily fluids, organs – or contaminated environments. Patients have a better chance of survival if they receive early treatment.
Initial flu-like symptoms can lead to external haemorrhaging from areas like eyes and gums, and internal bleeding which can lead to organ failure.
Dr Chan was meeting the leaders of the worst-affected countries – Guinea, Liberia and Sierra Leone – to launch a new $100m (£59m; 75m euro) Ebola response plan.
The plan includes funding the deployment of hundreds more health care workers to affected countries.
Meanwhile, up to 30 Commonwealth Games athletes from Sierra Leone are considering extending their stay in Glasgow amid fears over the Ebola virus.
The BBC has also learned a second Sierra Leone athlete, Samuel Morris, has been tested for Ebola and cleared by doctors in Glasgow.
Cyclist Moses Sesay has also tested negative for the virus.
Sierra Leone, where more than 200 people have died from the disease, has declared a public health emergency.
The outbreak – the world’s deadliest to date – was first reported in Guinea in February.
It then spread to Liberia and Sierra Leone, and a person who travelled from Liberia to Nigeria died of the virus shortly after arriving in Lagos last week.
Ebola kills up to 90% of those infected but patients have a better chance of survival if they receive early treatment.