Opinion | I Shudder to Imagine Kennedy Running Our Health Agencies.

The Senate has just confirmed as health secretary Robert F. Kennedy, a science denialist who once said there is no vaccine that is safe and effective, who has suggested that Covid might have been genetically engineered to spare Jewish and Chinese people and who spent more than 100 pages in his recent book breathing new life into the idea that H.I.V. does not cause AIDS.

All of this is nonsense, of course, but hardly a laughing matter. I am afraid for our country because I know what happens when science denialism comes into power.

In the mid-2000s, I lived in South Africa, then governed by President Thabo Mbeki, who was also no stranger to the ideas of AIDS denialists. Amid an explosive AIDS epidemic in the late 1990s, Mr. Mbeki stumbled, most likely in late-night surfing of the internet, onto the fringe view that H.I.V. doesn’t cause AIDS and that the antiretroviral drugs used to keep it in check — the same type of drugs I take every morning and have for almost 30 years — were poison.

Mr. Mbeki, in thrall to these ideas, many of which came from America, refused to allow antiretroviral therapy to be used in the country’s health system. His health minister, Manto Tshabalala-Msimang, recommended healthy eating, with lots of beets, ginger and garlic, to ward off sickness.

A Harvard study later found that at least 330,000 people died, and over 35,000 children were born with H.I.V. as a result of Mr. Mbeki’s reign of error on AIDS treatment policy.

We are at risk of seeing history repeat itself in the United States, with our own Manto Tshabalala-Msimang-in-waiting in Mr. Kennedy Jr., whose science denialism is a more pernicious variant of the South African version.

In his book “The Real Anthony Fauci,” Mr. Kennedy revives debunked canards about H.I.V. — like the idea that it is a “harmless passenger virus” and that gay men’s promiscuity and use of recreational drugs, and even antiretroviral drugs like AZT were the real causes of AIDS — while using the “I’m just asking questions” strategy to allow him to deny that he’s an AIDS denialist himself.

As a gay man living with H.I.V., I cannot tell you how grotesque and offensive all this is and how hard it is to wrap my head around the idea that Mr. Kennedy will now preside over AIDS research, care and prevention programs at federal agencies.

Mr. Kennedy’s science denialism has the potential to be worse than that of his South African counterparts. Because it’s not only his AIDS denialism we need to worry about, it is his rejection of vaccines and flirtation with the rejection of germ theory, a key foundation of modern biomedicine.

For all the dangers he presents, I’ve heard a lot of defeatism over the past few weeks as Mr. Trump has flooded the zone with executive orders and other actions, which have had their desired effect of overwhelming his opponents. We can’t beat back all this, the logic goes, we’ve got to accept our fate and find a way to accommodate this brave new world under Mr. Kennedy and President Trump.

But if South Africa holds a cautionary tale for us, it also shows us a way forward.

Twenty-five years ago, President Mbeki’s African National Congress had a lock on power and many in the party refused to break with him on AIDS — even if his policies were a death sentence for South Africans living with H.I.V. Bodies were piling up, while pills to save the dying were out of reach, as a matter of national policy. It all seemed hopeless. How was anyone going to fight, let alone prevail against the party of liberation, which freed South Africans from apartheid?

But there were many who weren’t willing to accept defeat, like Zackie Achmat, a founder of the Treatment Action Campaign to demand access to antiretrovirals. He visited me in New York in 2000 and inspired my move to South Africa in the first place.

Activists with Treatment Action Campaign organized in townships and rural areas, teaching themselves the science of H.I.V. to combat the lies their government were peddling, and using that knowledge as the lever to build a mass movement. They knew there were drugs that could save their lives. The South African Constitution guaranteed the right to health, and they wanted to live. They recruited help from AIDS doctors and nurses, scientists working on H.I.V., lawyers who knew the young nation’s constitution inside out. In the end, however, it was ordinary South Africans who made the difference.

The relentless campaign to confront the government’s views on AIDS kept both the president and his health minister in the hot seat for years. By the time that internal party politics forced President Mbeki and Minister Tshabalala-Msimang to resign, that activism had laid the groundwork for South Africa to establish the largest antiretroviral drug program in the world.

So there is always hope for something else, something better. It’s in ordinary people organizing like my comrades in the Treatment Action Campaign did, against the odds, because failure would come at too high a cost.

It’s in the lessons that many of us learned in the 1980s and 1990s in the United States when we were going to funerals week after week, when we refused to accept death without a fight.

Over the next few years, Americans who hope for something better will have to go toe-to-toe with this administration, at all levels of government, challenging its attacks on science in the courts, finding ways to protect public health through state and local action, educating our communities about what is going on and ways in which they can help push back so when our own Manto Tshabalala-Msimang leaves in disgrace, we can pick up and build from the ashes.

And it’s already happening: Court cases were filed in the first weeks of the administration to challenge harmful executive orders that would hobble National Institutes of Health research, people are downloading and saving data on H.I.V. and L.G.B.T. health that the Trump administration is scrubbing from Centers for Disease Control and Prevention websites. People are refusing to accept buyout offers to purge them from agencies where they’ve toiled on behalf of the American public for years.

In the bravest of examples, when Mr. Trump ordered foreign aid assistance to stop, workers at one U.S.-funded program in Sudan refused to comply — they weren’t willing to abandon 100 children to starvation. And yes, thousands of people organized to oppose the nomination of Mr. Kennedy, and though, unsuccessful, their efforts have left us better prepared for the struggle to come.

Yes, sometimes you persist and you fight “the long defeat.” Because as the health care justice champion Paul Farmer once said, you don’t turn your back on those who have the most to lose. And sometimes, just sometimes, you win.