Rio de Janeiro carnival goers celebrated the coming Olympics on Saturday and even turned fear of infection from Zika-carrying mosquitoes into an excuse to party.

Participants at one of the many street parties popping up ahead of the official carnival, which starts February 5, honored the city's hosting of the Summer Games in six months by dressing in ancient Greek garb.

Three people in New York have tested positive for the Zika virus, which has been blamed for a surge in babies born with abnormally small heads in Latin America, city officials said Friday.

All three had travelled to areas outside the United States where the mosquito-borne ailment is spreading rapidly, the New York State Department of Health said, without specifying where.

With the sting of a mosquito bite and a fever, many pregnant women may not know that they caught the Zika virus -- until it strikes their unborn child.

Now authorities in some Latin American countries are warning women to avoid getting pregnant, after thousands of cases of birth defects linked to the disease over recent months.

At least 39 people have died of swine flu in Russia since last month, according to AFP calculations based on official data, with more than half the cases announced in the last week.

Health authorities in the southern region of Volgograd told state news agency RIA Novosti on Friday that 11 people had died from the virus and that nearly 50 schools had declared a quarantine.

A new case of Ebola has been confirmed in Sierra Leone, the second since west Africa last week declared an end to the epidemic, the country and the World Health Organization said Thursday.

"There was a new confirmed case," WHO spokesman Tarik Jasarevic told AFP in an email, adding that the new case was the aunt of 22-year-old student Marie Jalloh, who was determined to have died of the virus on January 12.

Dozens of makers of medicines and diagnostic tests have joined together in an unprecedented effort to tackle "superbugs" — infections that increasingly don't respond to drugs and threaten millions of people in countries rich and poor.

Altogether, 74 drugmakers, 11 makers of diagnostic tests and nine industry groups have signed a groundbreaking agreement to work with governments and each other to prevent and improve treatment of drug-resistant infections. They plan to announce the new agreement Thursday at the World Economic Forum in Davos, Switzerland.

A U.S. judge charged five people Wednesday with trying to steal trade secrets from the British pharmaceutical group GlaxoSmithKline (GSK).

Of the five, two worked at a GSK research center in Upper Merion, Pennsylvania.

Eleven people have been killed by the swine flu virus in Syria since September, the country's health ministry said on Tuesday.

"Since September, 27 people infected with the H1N1 virus have been hospitalised. Eleven of them died," Ahmad Damiriyeh of the health ministry's division on chronic and contagious diseases was quoted in the state-run Al-Thawra daily as saying. 

At least 12 people have died of swine flu in Russia since last month, according to Agence France Presse calculations based on the statements of regional health authorities, as the virus gains ground in the country. 

Four swine flu-related deaths were recorded in the southern region of Rostov among the 120 reported cases of the virus in the area, authorities said Tuesday.

Women who carry an inherited fault in the BRIP1 gene are three times more likely to develop ovarian cancer than those without it, researchers said Tuesday.

The gene variant had already been linked to cancer of the ovaries, but the size of the additional risk has now been quantified in a study in the Journal of the U.S. National Cancer Institute.