BAMAKO, Mali (AP) - Mali's emerging Ebola crisis deepened Thursday as the government announced that a doctor had died from the disease, becoming the second health worker fatality linked to a single patient initially thought to have kidney disease. At least five people now have died from Ebola after coming into contact with a 70-year-old grand imam, who was brought to the Malian capital of Bamako from Guinea, the bordering country where the regional Ebola epidemic first began. The death of a 25-year-old male nurse at Clinique Pasteur who treated the imam first prompted health authorities to review past patients. The imam's family members who had brought him to Bamako all were later admitted to an Ebola clinic back in Guinea upon their return. Malian authorities are now following more than 300 people, including those who helped prepare the imam's body for burial after he succumbed to the disease. Health workers have been particularly vulnerable to contracting Ebola because of their close contact with the sick, who spread the virus through bodily fluids such as blood, urine and feces. On Thursday, a Cuban doctor who had contracted the virus in Sierra Leone was flown out of the country en route to treatment in Switzerland. Despite some improvements in Liberia and Guinea, the World Health Organization said Wednesday that the spread of Ebola remains "intense" in most of Sierra Leone. Associated Press writer Clarence Roy-Macaulay in Freetown, Sierra Leone contributed to this report.