When the police made an arrest Thursday in the 1979 disappearance of 6-year-old Etan Patz in New York, the tragedy underscored the unfinished searches for other children whose parents continue to hunt for them with photographs artfully retouched to transform baby faces into teens.

It was the case of Etan Patz that prompted the creation of the National Missing Children’s Day in 1983 on the anniversary of his disappearance on May 25. Three years later an international day was created on the same date to build awareness about missing children in other countries.

Etan Patz, who vanished while walking to his school bus alone in his SoHo neighborhood for the first time, was one of the first missing children ever to appear on a milk carton and became a turning point for parents who altered the way they raised their children and protected them from peril.

After decades of dashed hopes and conflicting clues, Pedro Hernandez, 51, a former bodega store stock clerk, was arrested Thursday on murder charges with a confession that he lured the boy into a shop with the promise of a soda, choked him in the basement and placed his body in a bag and dumped it about a block away in the open trash.

The police authorities said there was no physical evidence, but he had given a detailed, signed confession along with incriminating comments to others, including someone who tipped off a Missing Persons Squad that Mr. Hernandez spoke of killing a child in New York. He was held overnight Thursday under suicide watch and transferred to Bellevue Hospital Center on Friday morning. Whether that confession is indeed true remains to be determined.

The Etan Patz case had impact abroad because it slowly built awareness about the issue as it was changing enforcement strategies in the United States. A wait and see attitude about missing children eventually evolved into an aggressive Amber Alert system that enlisted the public into searches through television announcements and postings on electronic highway billboards.

Those strategies came later in Europe, prompted by several high profile cases, particularly the disappearance of Madeleine McCann. At age 3, she vanished in Portugal in 2007 while her British family was on a resort vacation.

“Every high-profile case, unfortunately, helps raise awareness of missing children and what people usually do not know is that those cases represent just a small percentage of the overall cases,” said Valeria Setti, a project officer with Missing Children Europe, a Brussels organization with member groups in 20 countries in Europe. More than 60 percent of missing children in Europe are runaways, most frequently teen girls, and 25 percent of disappearances involved parental abductions, she added.

The Madeleine McCann case inspired closer cross-border coordination, amid criticism of the slow response of the Portuguese police investigation. It also helped give rise to a new, confidential hotline, 116000, this month to report sightings of missing children and offer support and psychological counseling to parents in a crisis.

The free service is available 24 hours a day in 16 European countries, including Portugal, France, Spain and Germany. “I think that Europe woke up then and the institutions understood that they had to take some steps,” Ms. Setti said.

The McCann family, whose ceaseless energy has kept the case in the international spotlight, has also publicly supported the new help number, calling it a “lifeline” for parents and part of a shift in attitudes among politicians to provide more resources.

They are also among the families who have turned to specialists to transform the missing posters of their children into teens, releasing a photo this month of Madeleine where she is aged to look 9 years old.

Éric Mouzin, the father of Estelle who disappeared at age 9 in France in 2003, has also issued an age-enhanced photo of his daughter who was last seen walking home on a snowy January day. It was her case that helped give rise to France’s abduction alert system in 2006. Since it was introduced, it has been used 10 times and all of the children were found — eight as a direct result of the alerts, according to Missing Children Europe.

In his 2011 memoir, “Find Estelle,” Mr. Mouzin reflected anger about the “infinite slowness” of the investigation. This year his support group, Association Estelle, is not organizing any public demonstration in connection with International Missing Children’s Day. “We don’t have the energy,” he told Le Monde.

By DOREEN CARVAJAL / nytimes.com