"This year there's been one big home run and a lot of scratch singles." That's how Red Sox fan and editor-in-chief of the New England Journal of Medicine, Dr. Jeffrey Drazen, sums up the year-that-was in public health.

Zika was the home run of 2016. It got lots of attention. It created a lot of drama. And it had a significant public health impact this year, says Drazen, who is a professor at the Harvard T.H. Chan School of Public Health. The Zika outbreak prompted travel warnings throughout the hemisphere and sparked frantic efforts to develop a vaccine.

And then there are the "scratch singles." In baseball a "scratch single" is when a hitter barely hits the ball — "scratches" it — but still manages to get to first base. Drazen is talking about the non-glamorous work in public health that wins games over the long haul.

With ongoing efforts to combat mosquitoes and get people to sleep under bed nets, deaths from malaria continue to decline in Africa — down from more than 800,000 a year in 2000 to roughly 400,000 last year.

New HIV infections and fatalities have stabilized globally, although that still means that the virus spread to about 2 million more people in 2016 and killed another million. This flat-lining on HIV/AIDS is seen by some as a worrisome indication that progress against the epidemic has stalled. The more optimistic voices in the HIV world, however, point out that given the rapidly expanding population in Africa, where the bulk of new infections occur, the fact that numbers aren't rising illustrates a heroic effort to keep this epidemic from getting far worse through prevention, education and HIV treatment programs.

Middle Eastern Respiratory Syndrome or MERS refuses to die but appears to be slouching toward extinction. MERS has primarily been a Saudi Arabia problem thus far. Since the virus was first discovered in 2012, 1482 of the 1841 cases reported to the World Health Organization have been in Saudi Arabia. One significant exception came in 2015, when a MERS outbreak in Korea caused panic in Seoul, temporarily shutting down schools, hospitals and factories. The outbreak in Korea was sparked by a businessman who'd recently returned from the Middle East. And although transmission of the virus continues at only a low level in Saudi Arabia, there's no reason that a traveler couldn't trigger another outbreak like the Korean one somewhere else in the world.

But in baseball terms, MERS in 2016 was the slugger at the bottom of the batting order, still getting up to the plate, still a threat but not causing much concern.

On the good news front, there have been lots of little advances — promising stars emerging from the ranks of the minor leagues. "There's a new herpes vaccine for shingles that's 90 percent effective," Drazen says enthusiastically about a Glaxo Smith Kline vaccine that just wrapped up clinical trials. The GSK vaccine is far more effective than the roughly 50 percent offered by the only commercial shingles vaccine currently on the market.

"And guinea worm, we are almost close to eradicating that," Drazen adds. Guinea worm is a nasty tropical parasite that's spread by contaminated water. The worms pop out of people's legs like long, burning strands of spaghetti. The Carter Center, which has been one of the lead agencies in the effort to stamp out guinea worm, says there were fewer than two dozen cases in the first 10 months of 2016.

Rob Henry, a senior public health adviser with USAID's Neglected Tropical Disease (NTD) program, shares Drazen's outlook: "I think 2016 was an excellent year," he says.

"This year, for example, Guatemala was declared free of onchocerciasis — river blindness. That's a big one."

River blindness is a parasitic infection, spread by black flies, that causes excruciating itching and in severe cases blindness. The declaration that Guatemala is now free of the disease means that river blindness has been eliminated from everywhere in the Americas except one remote area in the Amazon along the border between Brazil and Venezuela.

River blindness is one of the seven neglected tropical diseases that USAID's NTD program focuses on. Lymphatic filariasis is another. Also known as elephantiasis, it can cause horrific swelling of the legs and scrotum.

"Cambodia this year got acknowledgement from WHO as having eliminated lymphatic filariasis as a public health problem," Henry says. "That's a big moment for Cambodia."

Henry says eliminating diseases like elephantiasis can't compete in the headlines with the fight against fatal conditions. But he too is a big believer in the power of small hits: "It's one thing to say you're out there saving lives but it's another thing to talk about how do you improve lives. How do you improve things to enable people to be able to make a living for themselves, for kids to be able to go to school, for people to be able to take care of their farms."

Mass de-worming programs supported by USAID can break the transmission cycle of the parasite that causes lymphatic filariasis. And Henry notes that significant progress is being made against this disease not just in Cambodia but across the tropics.

"In Africa, Togo is just about ready to be able to declare the elimination of lymphatic filariasis," he says. In the year 2000 in some parts of Togo up to 22 percent of residents were infected with the parasites that cause the debilitating swelling.

The other disease eradication effort that is tantalizingly close to victory but can never quite hit it out of the park is the campaign to end polio. And 2016 was a complicated year for the virus. On the one hand only 34 cases had been detected in 2016 as of this week. Unfortunately four of them were in Nigeria, which had previously been declared "polio-free" along with the rest of the African continent.

The new cases in Africa were found in areas recently liberated from Boko Haram. The insurgents barred health workers, destroyed health clinics and made routine immunization campaigns impossible.

Jeff Drazen says polio eradication is no longer a medical problem.

"We have the medical capacity to do this but it's become a political problem," he says. "It's not as much a medical challenge as it is a political challenge."

Or as the great baseball player Yogi Berra once said, "It ain't over 'til it's over."

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