Montgomery County’s health officer has raised new reservations about a plan to ease restrictions on backyard chickens in residential neighborhoods, citing elevated risk of human salmonella infection.

The proposal is part of a broad rewrite of the Montgomery zoning code, currently under review by the County Council’s Planning, Housing and Economic Development Committee. The poultry provision would allow chicken coops as close as 15 feet from a lot line. Current regulations require a 25-foot clearance from a lot line and 100 feet from any neighboring house. The measure reflects a growing interest in “sustainable” food sources to reduce the distances that people must travel. A number of localities have relaxed rules governing farm animals in residential areas.

At a June 23 hearing, County Health Officer Ulder Tillman offered few objections. But in a letter last week to Council President Nancy Navarro, Tillman raised a series of new concerns, many involving salmonella.

She cited an August report from The Centers for Disease Control and Prevention describing a multistate outbreak of human salmonella typhimurium infection linked to live poultry in backyard flocks. More than 300 people in 37 states were infected as of Aug. 15, 60 percent of them children 10 years old or younger. No deaths were reported, but 51 of those infected were hospitalized, according to the agency.

The CDC investigation linked this outbreak to contact with baby poultry from a New Mexico hatchery that supplies feed stores and mail-order customers nationwide.

“Because Salmonella can be present in the droppings of chicks and other baby birds and because the animals themselves usually do not show signs of illness, it is easy for people to let their guard down and run the risk of getting Salmonella,” Tillman wrote. Young children are especially at risk, she said, because their immune systems are still immature, and they are more likely to put their fingers and other items in their mouths.

“Based on this information, I do have reservations about the proposed modifications,” Tillman wrote. “Neither the County nor the State has an adequate registration and tracking mechanism for small-scale purchases of poultry.”

The committee is scheduled to meet Friday morning and is expected to discuss revising its recommendation on setbacks for chicken roosts.