UNITED NATIONS - A worrying increase in AIDS among adolescents is one of the reasons it is important not to become complacent about HIV and AIDS, Simon Bland, the New York director of UNAIDS, told reporters here Monday.

"We need to worry about adolescents -- we've seen a tripling in the death rate of adolescents since the beginning of the millennium," Bland at a press briefing here ahead of World AIDS Day on Dec 1.

"This is no time for triumphalism, it is not time for complacency," he said. "Each year still 2 million people become infected, over a million people die, and in some parts of the world there is little or no progress at all."

Bland said that HIV/AIDS is the second largest cause of death for adolescents globally and that there are 26 new adolescent infections every hour.

Adolescent girls are disproportionately affected, he said, making up seven out of 10 new infections globally, influenced considerably by high infection rates among girls in Sub-Saharan Africa.

"We know in Sub-Saharan Africa the vast-majority of new infections are among young women and girls," he said.

Half of these girls were in just six countries, South Africa, Nigeria, Kenya, India, Mozambique and Tanzania, he said.

Bland said that it was important to understand these differences and that there is no part of the world where the job of addressing AIDS is complete.

Bland said that recent figures from China were a "real concern." The Chinese Center for Disease Control and Prevention (China CDC) said that there were 575,000 people living with HIV/AIDS (PLWHA) by the end of October this year and 177,000 deaths.

He said UN AIDS would work with Chinese authorities to see what's happening in China and offer assistance.

World AIDS Day is an opportunity to think about the past but also to look to the future, said Bland.

"World AIDS Day is an important moment to reflect and to commemorate all those who have lost their lives to this disease," he said, "to reflect on the challenges that face us today, and those that lie ahead."

The Day is also an opportunity to reflect on progress made in the fight against HIV/AIDS. A lot has changed since the 1980s and 1990s when HIV/AIDS was considered an inevitable death sentence, said Bland.

For example, due to considerable efforts, the price of antiretroviral treatment has reduced from 10,000 dollars per patient per year to now around a hundred dollars per patient per year.

Also notably, Cuba was certified as being free of mother to child transmission earlier in 2015, he said.

Innovation such as rapid diagnostics have also made it easier to test for HIV and AIDS. Yet in this area much more progress is still needed. Of the estimated 37 million people living with HIV, around 19 million do not know their status, said Bland.

However, while infections and deaths from AIDS have decreased considerably from their peak in 2000 and 2001, respectively, Bland warned that this progress is fragile, unfinished and reversible.

Tackling the growing problem among youth, he said, would mean making sure that young people are empowered, he said. "The youth are going to be part of the solution and certainly need to have a stronger voice," said Bland.