Some people may retain awareness after they have technically died, according to an unusual study published on Wednesday into hospital patients who went into deep cardiac arrest.

In a boost for the long and frustrating quest for an AIDS vaccine, researchers on Wednesday unveiled molecular imaging of an elusive feature that helps HIV infect immune cells.

Haiti's cholera epidemic is still an emergency and a let up in response based on the decreasing number of cases could have "tragic consequences," a U.N. special envoy said Wednesday.

"I fear that the enormous progress we have made leads people to believe that the problem has been resolved. It is not resolved," Pedro Medrano, the U.N. coordinator overseeing cholera response in Haiti, told Agence France Presse in Washington.

The United States and Canada announced stepped-up airport screening measures Wednesday to look for passengers carrying Ebola, as the deadly virus killed a man in Texas and the worldwide toll neared 3,900.

The spillover of the virus -- with the first diagnosis in United States and the first case of infection in Spain -- has raised fears of contagion in the West.

The United Nations mission in Liberia announced on Wednesday a second infection among its employees of the deadly Ebola epidemic ravaging the impoverished west African nation.

France will introduce plain cigarette packaging in 2016, Health Minister Marisol Touraine said on Wednesday, as the country seeks to stub out high smoking rates in under-16s.

The United States will announce tightened controls on international travelers in the coming days to prevent Ebola from spreading on U.S. soil, health officials said Tuesday.

One of the scientists who discovered Ebola said Tuesday he was not surprised a Spanish nurse contracted the deadly virus, stressing it was impossible to be too careful when dealing with the disease.

Doctors in Spain hospitalized four more people and rushed to identify dozens of others at risk on Tuesday after a nurse was infected with the deadly Ebola virus, raising fears of contagion in Europe.

The European Union demanded answers about how the disease spread in a specialized disease unit, while health staff protested over safety failures.

Cigarettes and other tobacco products increase the risk of contracting a sexually transmitted virus linked to mouth and throat cancer, according to a study released Tuesday.

Oral human papillomavirus type 16, or HPV16, is found in 80 percent of throat cancers and is transmitted by oral sex. Tumors related to the virus have increased by 225 percent in the United States in the past two decades.