The AIDS pandemic is not a single global epidemic. Rather, it is a series of cascading, overlapping outbreaks of disease sweeping over communities the way waves pound relentlessly at a shore.
Those hardest hit are the most vulnerable, the marginalized and the disenfranchised: girls and women in countries where they have few rights; men who have sex with men where that is taboo; sex workers; intravenous drug users; members of minority groups such as aboriginals.
There is a realization of late that, if AIDS is ever going to be stopped, those marginalized groups must be targeted for prevention and treatment efforts, and they have been the focus of much discussion at the 17th International AIDS Conference in Mexico City.
Yet, for all the good intentions of the world's scientists, clinicians, community workers and activists, for all the grand statements about human rights, the largest of the marginalized groups has been callously ignored: People with disabilities.
About one in 10 people worldwide has a physical disability, about 650 million people. That many again, if not more, suffer from developmental or psychiatric disabilities.
There is no reason to believe that their HIV-AIDS infection rate is any less than other groups'. In fact, there is every reason to believe it is much higher.
What few studies have been done - and there has been a lot more research done on transgendered people with HIV-AIDS than on disabled people with HIV-AIDS - suggests that the infection rate is significantly higher, probably two to three times more than the able-bodied and sound of mind.
In most societies, the disabled are shunned, at best hidden away and pitied. They are invariably the poorest of the poor: denied education and employment opportunities; unlikely to access health care services; frequent victims of physical and sexual violence; far more likely to end up in jail, particularly if they have a psychiatric illness.
There can be no doubt that there is HIV-AIDS in the disabled community and probably at alarming high rates.
Yet, in the AIDS world, the disabled are invisible and voiceless. Hidden in plain sight.
Or at least they were until now.
Stephen Lewis, under the rubric of his latest charitable venture, AIDS-Free World, has taken on the cause of the disabled with HIV-AIDS, lending his powerful voice to a group he says is "lamentably neglected."
Winstone Zulu, a Zambian activist, has almost died a number of times from the effects of tuberculosis and HIV-AIDS. He has tasted discrimination in many ways.
But nothing, he says, is more humiliating and soul-destroying than having a disability.
"If you're sitting in a wheelchair, it's as if you don't exist," Mr. Zulu says.
The comments were made at the International AIDS Conference, but Mr. Zulu spoke from the audience because there was no ramp that allowed him access to the podium.
At a conference where inclusion is taken seriously - there is methadone for drug addicts, reserved spaces for people with HIV-AIDS to rest and booths for groups representing every conceivable sexual orientation - it is as if the physically disabled don't matter.
Mr. Zulu says the lack of access to the stage is symbolic of what is going on in the field, and that's tragic because the "main driver of the HIV-AIDS epidemic is denial."
Myroslava Tataryn, the adviser on disability and AIDS for AIDS-Free World, says that people with disabilities are being excluded from HIV-AIDS initiatives principally because of some hoary myths.
"There are widespread ideas that, somehow, because we have a disability, we don't fall in love, that we can't find partners and there is no way that we would have sex," she says. "Needless to say, these are erroneous misperceptions."
Ms. Tataryn, a young Canadian activist, has certainly not let her disability hold her back, in her personal or professional life.
Yes, people with disabilities have sex. They have children. (Three in every four people with disabilities in the developing world are women.) They get blood transfusions. They may inject heroin, abuse prescription drugs and drink alcohol to excess. (There is a strong correlation between mental illness and substance abuse.) As such, they are potentially at risk of contracting HIV-AIDS.
So where are the programs? When are we going to have targeted prevention and treatment programs for the disabled?
People with disabilities and HIV-AIDS have, for the first quarter century of the epidemic, been victims of double discrimination and shameful neglect.
The way they have been treated is a horrific embodiment of the axiom: There are none so blind as those who will not see.
It is time for the AIDS world to open its eyes.
TB and HIV-AIDS
Watch the mini-documentary Winstone Zulu Is Alive at