The Covid-19 pandemic has severely set back the fight against other global scourges like H.I.V., tuberculosis and malaria, according to a sobering new report released on Tuesday.

Before the pandemic, the world had been making strides against these illnesses. Overall, deaths from those diseases have dropped by about half since 2004.

“The advent of a fourth pandemic, in Covid, puts these hard-fought gains in great jeopardy,” said Mitchell Warren, executive director of AVAC, a nonprofit organization promoting H.I.V. treatment worldwide.

The pandemic has flooded hospitals and disrupted supply chains for tests and treatments. In many poor countries, the coronavirus crisis diverted limited public health resources away from treatment and prevention of these diseases.

Many fewer people sought diagnosis or medication, because they were afraid of becoming infected with the coronavirus at clinics. And some patients were denied care because their symptoms, such as a cough or a fever, resembled those of Covid-19.

Unless comprehensive efforts to beat back the illnesses resume, “we’ll continue to play emergency response and global health Whac-a-Mole,” Mr. Warren said.

The report was compiled by the Global Fund, an advocacy group that funds campaigns against H.I.V., malaria and tuberculosis.

Before the arrival of the coronavirus, TB was the biggest infectious-disease killer worldwide, claiming more than one million lives each year. The pandemic has exacerbated the damage.

In 2020, about one million fewer people were tested and treated for TB, compared with 2019 — a drop of about 18 percent, according to the new report.

The number of people treated for drug-resistant TB declined by 19 percent, and for extensively drug-resistant TB by 37 percent. Nearly 500,000 people were diagnosed with drug-resistant TB in 2019.

“We’ve been hit really hard on TB,” said Peter Sands, executive director of the Global Fund. “I’m afraid that inevitably means hundreds of thousands of extra deaths.”

India, which has the highest TB burden in the world, had resumed its pre-Covid rate of TB diagnoses by late 2020, but the outbreak this past spring is likely to have reversed that progress, Mr. Sands said.

A drop in TB diagnoses can have far-reaching consequences for a community. One person with untreated TB can spread bacteria to as many as 15 people each year.

Compared with 2019, the number of people in 2020 who sought testing for H.I.V. declined by 22 percent, and the number who opted for H.I.V. prevention services fell by 12 percent. Medical male circumcision, thought to slow the spread of the virus, decreased by 27 percent.

“Because there isn’t a cure for H.I.V., every single person who gets infected is a long-term impact,” Mr. Sands said.

Diagnoses of malaria fell by a small amount, according to the report. Most countries were able to adopt measures that limited the impact on diagnosis and treatment.

As many as 115 million people have been driven into extreme poverty because of Covid-19, further limiting their access to treatment and support. In some countries, school closures and lockdowns made it particularly difficult for adolescent girls and young women to receive health services.

There were a few glimmers of hope amid the bleak news: The crisis forced health agencies and ministries in many poor countries to adopt innovations that may outlast the pandemic. Among them: dispensing to patients multi-month supplies of TB and H.I.V. drugs, as well as condoms, lubricants and needles; using digital tools to monitor TB treatment; and testing simultaneously for H.I.V., TB and Covid-19.

For example, in Nigeria, community health workers who tested people for Covid also looked for cases of H.I.V. and TB. As a result, the country became one of the few to see a rise in H.I.V. diagnoses compared with 2019.

In Ouagadougou, Burkina Faso, community health workers on motorbikes delivered insecticide-treated bed nets door to door, rather than distributing them from trucks in village squares. This approach allowed them to reach more households than before and helped to cut down the number of malaria infections.

“It’s a bit more expensive” to deliver nets to individual households, Mr. Sands said, but “that was an investment that was clearly worth doing.”

To minimize the impact of the pandemic, the Global Fund has spent about $1 billion more than its usual budget, Mr. Sands said. In March 2020, the organization released $500 million to help countries cope; as of August 2021, it had raised $3.3 billion for use in 107 countries.

The funds have been used to shore up health systems, to provide tests, treatments and oxygen, and to give personal protective equipment to health care workers.

Donors have committed to provide another $6 billion for H.I.V. and $2 billion for TB over the next three years, Mr. Sands said.