But there has been progress in the fight against some other major killers.

Ashish Jha, a physician with the Harvard T.H. Chan School of Public Health and the director of the Harvard Global Health Institute, said there have been major drops in the mortality of children under 5 (down more than 50 percent in the last three decades), and he pointed to other encouraging advancements:

the halving of deaths of women at childbirth

significant decreases in death from malaria

a turnaround in the H.I.V. epidemic

increased life expectancy in every country

Funding science research has led to new therapies, and global funding programs like Pepfar in the United States have made those medicines widely available, Dr. Jha said. Pepfar, begun under the administration of George W. Bush to combat the H.I.V. epidemic, says it has saved more than 16 million lives, primarily in Africa.

Establishing regional organizations to respond to outbreaks is also important, “as the 2014 to 2015 West African Ebola epidemic taught us,” said Peter Piot, a physician and director of the London School of Hygiene and Tropical Medicine.

The introduction of the Africa Centers for Disease Control and Prevention in 2017 “marks an important step toward strengthening capacity and preparedness across the continent,” he said.

Some investments may not even seem to focus on health. Dr. Jha singled out girls’ education as the thing he’d invest in first. “Beyond its big effects on economic prosperity, it also leads to smaller family sizes, lower infant mortality, more stable families and communities, and likely lower levels of disease burdens like H.I.V.”

Improving health care systems can be crucial. Shoddy ones can actually cause harm — never mind failing to heal the sick. A 2012 study in Health Affairs showed that in rural areas of India, two-thirds of health professionals had no medical qualifications whatsoever. Incorrect diagnoses and treatments were more common than correct ones.