A yellow fever outbreak in Angola has killed 51 people out of 241 suspected cases, in the first epidemic of the disease to hit the country in 30 years, official statistics showed Monday.

The center of the outbreak is the capital Luanda's eastern suburb of Viana where 29 deaths and 92 cases have been reported over the last six weeks, national director of public health Adelaide de Carvalho said.

Men are twice as likely as women to get cancer of the mouth and throat linked to the human papillomavirus, or HPV, one of the most common sexually transmitted infections, researchers say.

For men, the risk of HPV-driven cancers of the head and neck rise along with the number of oral sex partners, researchers said Friday at the American Association for the Advancement of Science (AAAS) annual meeting in the U.S. capital. 

The Zika virus, linked to a surge in infants born with abnormally small heads, is likely to spread this year to Brazil's densely populated cities where it has barely surfaced, a top health official told Agence France Presse.

Zika has struck hard in hot and humid southeastern and central Brazil, but largely spared bigger cities like Sao Paulo or Rio de Janeiro, said Claudio Maierovitch, head of the communicable diseases surveillance department at the Ministry of Health.

American scientists traveled to Colombia to investigate the mosquito-borne Zika virus and help find a vaccine for the disease that is plaguing Latin America, the U.S. ambassador to Bogota said Friday.

The U.S. experts are studying "the possibility of a vaccine" alongside specialists from the Colombian Health Ministry, Ambassador Kevin Whitaker said from Bogota, capital of the second worst-hit nation.

Brazilian laboratories say delays in providing kits to test for mosquito-borne dengue have forced them to store patient blood samples until the kits are delivered.

In Sao Paulo, the state government's Adolfo Lutz Institute says in a statement it has not received any of the 2,500 kits it requested from the Health Ministry five months ago.

Dementia rates in the United States may be falling, an influential study released Wednesday said, offering hope that some cases of the disease might be delayed or even preventable.

The findings, published in the New England Journal of Medicine, appeared to defy fears over an explosion in the disease among the country's aging population.

For health workers battling Zika across much of Central America, the immediate menace is not the mosquitoes that transmit the virus. It's the gangsters who control the streets, and sometimes threaten their lives.

Armed and well-organized street gangs known as maras exert near-total control over entire neighborhoods, using sentries to track everyone who comes and goes. In some cases, they deny access to health crews they suspect of working with police or a rival gang.

For the thousands of Syrian refugees expected to arrive in the U.S. in coming months, the first order of business will be securing the basics — health care, jobs, education and a safe home.

But what organizations helping resettle them might not be prepared for, and what refugees themselves might be in denial about, is the need to treat the mental scars of war, experts said.

After Dr. Saleem Haj-Yahia performed the first-ever successful artificial heart transplant in the West Bank last month he was greeted with flowers, balloons and cheering crowds and publicly praised by Palestinian President Mahmoud Abbas.

The British-educated cardiologist has become a media darling in his native land and now speaks of ambitious plans to raise the level of the entire Palestinian medical infrastructure.

President Barack Obama on Monday asked for more than $1.8 billion in emergency funds to tackle the fast-spreading Zika virus at home and abroad.

The mosquito-borne illness has surged through Latin America, prompting fears that clement spring weather could bring an explosion in cases.