The infection is strep, and the condition it appears to trigger in a small number of children is called PANDAS—short for pediatric autoimmune neuropsychiatric disorder.

Symptoms come on suddenly and can include:

-- obsessive-compulsive behaviors

-- mood swings

-- hyperactivity

-- separation anxiety

-- joint pain

-- tic disorders such as Tourette’s Syndrome.

Some doctors still aren’t sold on the idea that the bacteria that cause strep throat can, in some children, attack the brain and lead to severe neuropsychiatric problems.

The condition is under study by scientists at the National Institute of Mental Health and several academic institutions.

“There are still some people who don’t believe in it,” said Dr. David Band, a psychiatrist in Ashburn.

Band said he regularly treats children with PANDAS by prescribing a long course of antibiotics. Researchers at the National Institutes of Mental Health are evaluating the effectiveness of long-term antibiotics for children diagnosed with PANDAS, the NIMH website says.

The site recommends cognitive behavioral therapy and some medicines to minimize obsessive-compulsive behaviors and tic disorders associated with PANDAS.

Parents whose children are affected, meanwhile, are pushing for greater awareness of the condition and for more research that might zero in on effective treatment.

'A BATTLE AT EVERY STEP’

Parents whose children suffer from PANDAS describe symptoms that range from violent rages to multi-hour crying jags, eating disorders, and the compulsion to follow certain rituals that make it impossible to attend school.

Beth Maloney’s son Sam, for example, the subject of the book “Saving Sammy,” suddenly could not use the front door of his house. Leaving the back door, he would hop upon the stones lining the house’s walkway one by one. If he slipped and landed on the crushed-stone path, he would return to the beginning and start again. It could take hours for him to get from his bedroom to the car, if he could be persuaded to leave the house at all.