Figures released on World AIDS Day show infection and death rates are falling, but experts warn many people spend years without knowing they are infected.
Europe has made good progress towards a goal of eliminating AIDS by 2030 but late diagnosis of HIV remains a significant problem, new figures reveal.
The data released to mark World AIDS Day on Tuesday, December 1 showed new diagnoses in the EU and European Economic Area (EEA) had declined by 9% since 2010.
AIDS cases declined by nearly a quarter in the same period, the figures show.
The vast majority of new cases are emerging in Eastern European countries, particularly Russia and Ukraine.
But the European Centre for Disease Prevention and Control (ECDC) said the number of undiagnosed HIV cases was increasing.
It can take three years for the average European person infected with HIV to be diagnosed, it added.
"Too many people throughout the [region] are diagnosed late (53%), increasing their risk of ill health, death and onward HIV transmission," the ECDC said.
"The high number of AIDS diagnoses in the East confirms that late HIV diagnosis remains a major challenge."
HIV positive people who are not aware they are infected have no access to drug treatments and risk unknowingly passing the virus onto others.
Nearly 137,000 people were diagnosed with the virus in Europe in 2019 — 25,000 of these were in countries of the European Union and European Economic Area (EEA).
The highest number of cases per 100,000 people in Western Europe were reported in France, the United Kingdom and Germany.
No cure, but effective treatments
HIV began spreading around the world four decades ago and killed millions of people in the 1980s and 1990s.
The virus damages cells in the immune system, weakening people's ability to fight everyday infections.
When a person's immune system becomes severely damaged, they develop AIDS, which can be life-threatening.
There is no cure for HIV, but drug treatments are now extremely effective at allowing most people to live healthy lives.
Winnie Byanyima, director of the United Nations programme UNAIDS, said it was important the world did not repeat "the same mistakes it made in the fight against HIV" when responding to COVID-19.
"Even today, more than 12 million people are still waiting to get on HIV treatment and 1.7 million people became infected with HIV in 2019 because they could not access essential services," she said.
One of the world's Sustainable Development Goals is to eliminate AIDS at a public health threat by 2030.
Byanima said the goal was "already off track before COVID-19", adding: "We must end the social injustices that put people at risk of contracting HIV. And we must fight for the right to health."