The Ebola outbreak in West Africa is accelerating and could grow six times larger to infect as many as 20,000 people, the World Health Organization said Thursday. The U.N. health agency unveiled a new road map for containing the virus, and scientists are fast-tracking efforts to find a treatment or vaccine.

Ebola has menaced Africa for 40 years, but previously struck in remote villages and was contained fairly quickly. This time, it has spread to major cities in four countries, provoking unrest as whole neighborhoods and towns have been sealed to the outside.

Ebola-hit nations met for crisis talks on Thursday as the death toll topped 1,500 and the World Health Organization warned that the number of cases could exceed 20,000 before the outbreak is stemmed.

Nigeria announced that the virus had reached its oil-producing hub, dashing hopes that the country had successfully contained it to its biggest city, Lagos.

The international response to West Africa's Ebola outbreak is "dangerously inadequate," said the emergency coordinator for Doctors Without Borders (Medecins sans Frontieres) in Sierra Leone on Wednesday.

"The Ebola outbreak has been out of control for months, but the global health community has taken a long time to react," wrote nurse Anja Wolz in the New England Journal of Medicine.

Emotions connected to memories can be rewritten, making bad events in the past seem better and good things appear worse, scientists from Japan and the United States have found.

The discovery of the mechanism behind the process helps to explain the power of current psychotherapeutic treatments for mental illnesses such as depression or Post Traumatic Stress Disorder (PTSD), they said, and could offer new avenues for psychiatric help.

More than a dozen landmarks across the U.S. and Canada will light up to promote next week's "Stand Up to Cancer" telethon.

Organizers say the buildings that will be illuminated starting Thursday include Rockefeller Center in New York, Toronto's CN tower and the Wrigley Building in Chicago.

Japanese health officials said Thursday that three young people have contracted dengue fever, the first such infections in the country in nearly 70 years.

The three are suspected of having contracted the disease when they were bitten by mosquitos in Yoyogi Park in central Tokyo, officials said.

India has asked U.S. soft drinks giant PepsiCo to reduce the sugar content of its sodas as the country battles growing levels of obesity and diabetes.

PepsiCo chairman Indra Nooyi met food processing industry minister Harsimrat Kaur Badal during a visit to India on Tuesday to discuss its plans for healthier options and investing in India.

A World Health Organization (WHO) employee who has contracted Ebola arrived in Germany Wednesday, the first patient with the virus to be treated in the country, officials said.

A plane carrying the patient -- a Senegalese epidemiologist who was infected in Sierra Leone -- touched down at the airport of the northern city of Hamburg and was to be taken to a hospital isolation ward.

Researchers in Japan have been unable to replicate experiments that were hailed earlier this year as a "game-changer" in the quest to grow transplant tissue, amid claims evidence was faked, a report said Wednesday.

In a scandal that rocked Japan's scientific establishment, Riken -- a research institute that sponsored the study -- launched an independent experiment in April to verify research published by scientist Haruko Obokata and her colleagues earlier this year.

Venezuela's socialist government is sounding the alarm about growing waistlines in a country where record food shortages are making it harder to put healthy meals on the table, prompting many people to fill up on empty calories.

Authorities launched a public relations campaign Tuesday to halt a steady rise in obesity that threatens to lead to a costly, public health crisis if left unchecked.