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When Ebola hit Uganda two years ago -- the third outbreak in a dozen years -- the president quickly went on TV and urged Ugandans to avoid touching each other. Health officials speedily quarantined people. The quick reactions by authorities and ordinary people helped snuff out that outbreak with only 17 deaths.

Over the decades, Ebola cases have been confirmed in 10 African countries, including Congo where the disease was first reported in 1976. But until this year, Ebola had never come to West Africa. When people began dying there in March in an outbreak that on Friday escalated into an international public health emergency, governments and ordinary citizens didn't know what they were confronting or how to respond, allowing the virus to spread out of control.

Some five months ago, deep in the steamy forests of southern Guinea, people began developing fevers with body aches, diarrhea and vomiting, which are some of the symptoms of the virus. Others might also progress to internal and external bleeding.

Even when they died, relatives touched and washed the dead, unaware that cleaning up vomit, diarrhea and handling soiled clothing is very risky because the virus spreads through contact with bodily fluids.

Malaria -- a common killer in Africa -- was believed by some families to be the cause of death. As more people became gravely ill, some desperate relatives took their loved ones to the distant capital in search of better medical care, jammed into minivans or other transportation. People who came into contact with those who showed symptoms also became infected, and they in turn infected other people as they traveled freely.

Soon, people in the capital, Conakry, were getting sick.

By late March, Doctors Without Borders announced that Guinea faced an "unprecedented epidemic" of Ebola.

In early April, fear was sweeping through not only Guinea but neighboring Liberia, where deaths had also started occurring. When one lady fell in in Liberia, she was taken not to a hospital but to a church for divine intervention. She soon died. In Guinea, passengers fled a bus after an elderly man vomited on board.

"It took them time to realize it was Ebola," said Ugandan government epidemiologist Francis Adatu, who has been involved in tackling Ebola outbreaks in Uganda. "There was a delay in zeroing in and knowing that it is an Ebola epidemic."

"If you have Ebola contacts freely walking in the villages, then you have a serious problem," he said.

The West Africa outbreak also escalated because it affected cities and people are moving fairly freely across borders. In most past Ebola outbreaks, the people who got infected were in remote communities.

Local health authorities initially had no idea what they were dealing with and there was no community trust of the aid workers who encouraged isolation of patients from their families, said Michael Osterholm, a University of Minnesota professor who advises the U.S. government on infectious disease threats.

In previous Ebola outbreaks elsewhere in Africa, he said, "there was more belief they could bring it under control. People there saw these people came in in white suits and that in fact they could stop it. In Western Africa, there's no experience with this. Who are they to believe this could make any difference?"

While the 2012 outbreak in Uganda was effectively contained within weeks, the West African outbreak has now killed nearly 1,000 people in Guinea, Liberia, Sierra Leone and Nigeria. The World Health Organization on Friday declared the outbreak to be an international public health emergency that requires an extraordinary response to stop its spread.

The 17 deaths in Uganda that occurred two years ago were far fewer than previous outbreaks in the country, so hard lessons were being learned.

Uganda's first Ebola outbreak, in 2000, killed more than 220 people in about five months, and those deaths were largely blamed on the sort of official misjudgments and local ignorance seen in the Ebola crisis in West Africa.

In subsequent outbreaks, Ugandan health officials and aid groups moved more quickly to quarantine people who had had direct contact with those sickened by the disease. People were even encouraged not to properly bury their dead if they were victims of Ebola.

In July 2012, after an Ebola outbreak started sickening people in western Uganda, President Yoweri Museveni urged Ugandans to stop shaking hands. Casual sex was a risk, he said on national television.

Sam Kigozi, a shopkeeper in the Ugandan capital of Kampala, said he was so alarmed after Museveni issued the warning in July 2012 that he heeded the recommendations.

"I remember very well when Museveni warned us and the fear that I felt," he said Friday. "I decided no more shaking hands, no more playing around until Ebola was over. It was very serious."