PALATKA, Fla. — In this sleepy, riverside town in northeast Florida, 86-year-old Betty Wills sees the advertisements of obstetricians and gynecologists on the main road’s billboards and has found specialists ranging from cardiologists to surgeons in the phone book.

But there’s not a single geriatrician — a doctor who specializes in treating the elderly — in all of Putnam County, where a fifth of the county’s 74,000 people are seniors.

“I looked,” Wills said. “I didn’t find one.”

It’s a nationwide shortage and it’s going to get worse as the 70 million members of the baby-boom generation — those now 46 to 65 — reach their senior years over the next few decades.

The American Geriatrics Society says today there’s roughly one geriatrician for every 2,600 people 75 and older. Without a drastic change in the number of doctors choosing the specialty, the ratio is projected to fall to one geriatrician for every 3,800 older Americans by 2030. Compare that to pediatricians: there is about 1 for every 1,300 Americans under 18.

Geriatricians, at their best, are medicine’s unsung heroes. They understand how an older person’s body and mind work differently. They listen more but are paid less than their peers. They have the skills to alleviate their patients’ ailments and living fuller, more satisfied lives.

Though not every senior needs a geriatrician, their training often makes them the best equipped to respond when an older patient has multiple medical problems. Geriatricians have expertise in areas that general internists don’t, including the changes in cognitive ability, mood, gait, balance and continence, as well as the effects of drugs on older individuals.

But with few doctors drawn to the field and some fleeing it, the disparity between the number of geriatricians and the population it serves is destined to grow even starker.