At least 1,550 people have died of Ebola and more than 3,000 have been infected since the virus was detected in the remote jungles of southeastern Guinea in March, and quickly spread across the border to Liberia and Sierra Leone.
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The World Health Organization warned on Thursday the actual number of cases could be up to four times higher and said that a total of 20,000 people could be infected before the outbreak ends.
In the Guinean city of Nzerekore, riots broke out on Thursday night over rumors that health workers had infected people with the Ebola virus, a Red Cross official and residents said.
A crowd of young men, some armed with clubs and knives, set up barricades across the southern city on Thursday and threatened to attack the hospital before security forces moved in to restore order.
Gunshots were fired and several people were injured, said Youssouf Traore, president of the Guinean Red Cross.
"A rumor, which was totally false, spread that we had sprayed the market in order to transmit the virus to locals," Traore said. "People revolted and resorted to violence, prompting soldiers to intervene."
Local Red Cross workers had to flee to the military camp with their medical equipment. Another resident said the security forces were preventing people leaving their neighborhoods overnight.
More than 400 people have died in Guinea, though the infection rate is slower than in neighboring Liberia and Sierra Leone.
Senegal's Health Minister Awa Marie Coll Seck said the country's first case was a Guinean student who turned up for treatment at a hospital in the capital Dakar on Tuesday, concealing the fact that he had close contact with victims in his home country.
Authorities in Guinea had been searching for the young man for three weeks since he evaded surveillance, the minister said. Tests at the Pasteur Institute in Dakar showed him positive for the disease.
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"We are tracing his whole itinerary and also identifying anyone who had contact with the patient who now that he has been diagnosed is much more cooperative and supplied all the necessary information," the minister said.
In an attempt to prevent the spread of the virus, Senegal last week banned flights with three of the affected countries and shut its land border with Guinea.
In the latest sign that the outbreak is spinning out of control, the WHO said on Friday that the number of Ebola cases rose by the highest weekly amount since the epidemic began in Guinea, Liberia and Sierra Leone.
The WHO this month classified the Ebola outbreak as an international health emergency. On Thursday, it unveiled a $490 million road map to bring the outbreak under control over the next nine months, saying it was a global health issue.
In Sierra Leone's capital Freetown, a new WHO-backed mobile laboratory opened this week to test local cases, speeding up the response time.
But often financial pledges have not translated into more clinics and staff on the ground, said Jorge Castilla, epidemiologist with the European Commission's Humanitarian Aid and Civil Protection Department.
"I've seen many declarations, I see treatment centers on the maps but I know they are not working," he said in an interview after a trip to the affected countries.
Suspicion of health care workers has dogged government responses to the Ebola outbreak across West Africa.
They are often clad from head to toe in plastic protective gear and wearing protective masks, and many locals have shunned their assistance, often preferring to die in their own homes.
Unknowingly, many health care workers have contracted the virus themselves and infected the very communities they are seeking to help. So far, more than 120 health care workers have died in the epidemic. Liberia reported five new cases of infection among them in a single day this week.
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