According to the CDC, almost half a million Americans have died from Aids - almost 10 times as many as those who lost their lives in Vietnam.
Few people took note when, on 5 June 1981, a US Government bulletin noted a strange disease ravaging a number of gay men in Los Angeles.
Nobody could have foreseen then how the disease, soon to be named Acquired Immunodeficiency Syndrome (Aids), would take its grip on the world.
And now, 20 years later, with no real cure and no vaccine still, the toll of Aids has been staggering - 22 million people are known to be dead, and that figure is just a fraction of those living with the virus.
The huge majority of those infected don't even know it, says the United Nations' Aids agency (UNAids), meaning they may unknowingly infect others.
According to the CDC, almost half a million Americans have died from Aids - almost 10 times as many as those who lost their lives in Vietnam.
Last year, the US government declared Aids a threat to national security.
But the brunt of the disease has been borne in Africa, where Aids has etched such a deep impression that it has reshaped economies and populations.
Up to 30% of adults are infected in many sub-Saharan countries, and one in nine of all South Africans infected.
"The worst is yet to come," says Dr J Garcia Calleja, an epidemiologist with UNAids.
"There's no reason to think the situation is going to improve [in the short term]."
Behaviour change
The tremendous impact of the disease has not been confined to death tolls but has also altered the social landscape through behaviour change.
The carefree abandon of the sexual revolution of the '60s has given way to a generation grilled with safe sex messages.
Countries that once shied away from discussing sex publicly, such as Thailand, now routinely talk about condoms.
Aids has exposed deeply-hidden or marginalised behaviour, including drug injection, prostitution and homosexual sex.
But the disease has also helped spur huge advancements in the understanding of the immune system and viruses.
Politics and inequality
The scientific progress has not been enough to tackle Aids however, because the shape and scale of the epidemic has been driven by social inequalities and directed by politics.
Poverty, large-scale migration, war, poor educational levels and untreated sexually transmitted diseases have all fuelled the epidemic.
Governments have also been deeply reluctant to grapple with certain social problems, such as drug use, which lies behind the bulk of new HIV infections in many countries, including Russia, Vietnam and Malaysia.
The epidemic in most Asian countries first began among drug users, where infection rates soared from 1% to 40% among some drug-injecting communities in just one year.
Africa's burden
Africa though, has been the most blighted by Aids.
"Everybody [there] has some relative who is affected by HIV," says Dr Calleja.
"It has strained health services and reduced life expectancy."
Zimbabwe will have zero percent population growth next year due to Aids.
As Aids affects young and mobile adults, the disease has a socioeconomic impact, which has been felt by some industries, such as mining and banking, where there has been a problem with labour supply.
In some villages in the continent, a generation of adults has almost been wiped out; their children orphaned.
Experts say what has happened in Africa, which took two decades, is only just beginning in Asia, where the disease is still very young.
New infections in China, for example, have only been seen in the last two years. A huge blood scandal which has infected hundreds of thousands in the country is only now unfolding.
Twenty years after the advent of Aids, we may be only seeing the beginning.