For years, whenever Lucy Chesire, an HIV and tuberculosis activist, traveled to the United States from Kenya to meet with members of Congress, she kept one thing quiet at the airport: her own HIV status.

The United States barred most carriers of the virus from visiting the country, so Chesire, 39, never told immigration officials that she had it, even as she lobbied to overturn the ban during her annual visits here.

Two years ago, it was lifted. “For me, it was the biggest news that ever happened,” said Chesire, who this week will join tens of thousands of visitors from around the world — many of them HIV positive — to attend the 19th International AIDS Conference, which starts Sunday at the Walter E. Washington Convention Center and runs for six days.

It is the first time in 22 years that it will be held in the United States; organizers had stopped scheduling it here during the ban.

With more than 21,000 people from 177 countries registered, and thousands more expected to come to town without registering, it is expected to be the largest such gathering since the International AIDS Conference began in 1985. Conference attendees will fill about 6,000 hotel rooms and additional space in hostels, bed and breakfasts, and on the couches of friends and volunteers.

Official speakers include Secretary of State Hillary Rodham Clinton, Elton John, Bill Gates, Bill Clinton, Nancy Pelosi, Whoopi Goldberg and leading AIDS scientist Anthony Fauci, director of the National Institute of Allergies and Infectious Diseases at the National Institutes of Health.

Others in town for the conference include Jamar Rogers, an HIV-positive former “American Idol” contestant, who will perform at the convention center Monday, and Timothy Ray Brown, who appears to be the first person to have been cured of the virus, through bone marrow transplants he received for leukemia.

Holding the conference here has particular resonance, activists say, because HIV/AIDS is at epidemic levels in the District. About 2.7 percent of city residents older than 12 were living with HIV or AIDS in 2010, according to the latest annual report, released last month.

“What you see now in the District, the numbers are scary,” said Kareem Murphy, a local lobbyist who is a member of Metropolitan Community Church of Washington, which will serve as a meeting point for conference attendees.

“The city feels like it’s asleep to the reality of the existence and prevalence of HIV/AIDS,” Murphy said, adding that many of the city’s hardest-hit populations are in areas far from the center of power.

The District was chosen in part for this reason, said Chris Beyrer, professor of epidemiology at Johns Hopkins University who is on the governing council of the International AIDS Society. “We try and select cities where we can use the conference as a tool to try to engage awareness in the local population,” he said.

To help local underserved areas benefit from the conference, the DC Community Coalition has sold day passes at a reduced price of $75 a day. “When national events happen in our city, we often forget the neighborhoods,” said Christine Campbell, vice president of national advocacy and organizing for Housing Works, an advocacy group for people with HIV and AIDS.

For HIV-positive people living in the Washington area, holding the conference here is particularly meaningful.

“I’ve always been very involved in the HIV community, and honest to God, I’ve never been a part of anything this big,” said Sidney Robertson, 42, an HIV-positive hotel facilities manager who moved to the District last year from Charlotte.

More than 8,800 participants are from the United States; countries that have been hit hard by the epidemic, such as South Africa and Nigeria, are also sending large numbers. There have been 160 visa denials, according to conference organizers.

Worldwide, 34 million people are HIV-positive, and around 30 million have died of AIDS. In the United States, more than 600,000 have died of AIDS and around 1.1 million are infected, with around 50,000 new infections every year.

Unlike most conferences in Washington, this one will spill into the surrounding area.

Along with panel discussions on the latest developments in AIDS research and policy, the convention center will host a Global Village that is free and open to the public. The 190,000-square-foot area will feature debates and panel discussions as well as art exhibits and theater and musical performances.

“It will serve as the conference’s centerpiece for community and civil society,” said Global Village coordinator Joe Elias.

Affiliated events are being planned across the city, including a benefit production of “The Normal Heart,” Larry Kramer’s play about AIDS, at the Arena Stage on Monday and a display of parts of the 48,000-square-foot AIDS quilt on the Mall.

Local businesses and organizations are hosting non-affiliated events, including several marches. A Keep the Promise 2012 march, sponsored by the international nonprofit group AIDS Healthcare Foundation, will begin at 2 p.m. Sunday at the Washington Monument and will include speakers such as the Rev. Al Sharpton, Cornell West, Tavis Smiley, Wyclef Jean and Margaret Cho.

The march will be more of a rally than a protest, said Jason McCall, one of its organizers, adding that it will focus on shortcomings in AIDS policy such as “the lack of access to HIV testing, treatment and prevention, wavering political commitment to funding the global AIDS response, and excessive AIDS drug pricing by pharmaceutical companies.”

While there are likely to be people protesting at the marches and at the conference itself, the nature and scale of the protests have changed since the last time the conference was held in the United States, said Bill Arnold, chief executives of Community Access National Network, a national AIDS nonprofit group.

“There was more at stake,” said Arnold, who has been an AIDS activist since 1985. “People were out there who were going to die, and they didn’t like that.” With drugs available to manage the disease, “the fire in the belly piece is less alive in today’s people living with AIDS than it would have been 15 years ago or 20 years ago,” he said.

But, he added, “it’s 30 years on and we’re still behind the curve, both domestically and internationally, and I expect that some sessions may get interrupted by some groups who feel very strongly about that.”

Protests have already begun: Police said nine people were arrested Wednesday near the Capitol. Demonstrators had chained themselves to 50-foot tripods and hoisted themselves in the air to bring attention to the fight against AIDS, said activist Lucile Scott.

A “Psychedelic Hookers Ball” at Ziegfeld’s Secrets, one of a handful of places in the country where men may legally dance nude, is meant to draw attention to the situation of sex workers and intravenous drug users — two populations that have a high incidence of HIV transmission and who still face restrictions on entering the United States.

Some at the conference will be carrying red umbrellas, an international sex workers’ symbol.

Mariko Passion, a singer and sex worker in her 30s from Los Angeles, has solicited online donations from other sex workers so she can attend the conference and perform at the Global Village, but has fallen far short of her $2,500 goal. “I’m looking to decriminalize prostitution at the policy level,” she said, adding that if she makes it to the conference she will subsidize her trip by taking clients in the Washington area for $250 to $300 an hour. She said she is not HIV-positive.

For Appolinaire Tiam, technical director of the Elizabeth Glaser Pediatric AIDS Foundation in Lesotho, a country with one of the world’s highest rates of HIV infection, the choice of the nation’s capital as host city for the event was significant.

“The U.S. has invested a lot into HIV,” said Tiam, who arrived two weeks ago from Lesotho. “It’s good to have this conference in the back yard here, so the American people can see and touch and feel what we are actually talking about.”