In Milwaukee, 125 people have contracted HIV or syphilis in one of the largest HIV clusters the city has ever seen.

A “cluster” is an unexpectedly high incidence of a disease in a short period of time and close together, often among people connected in some way. If a cluster gets big enough, it’s called an outbreak, which is what Michael Gifford of the AIDS Resource Center is already calling this cluster.

Public health experts said that this cluster is important because of how many young people – including many high school students and three babies born with syphilis – are in it.

“It’s a really big deal,” said public health consultant Melissa Ugland. “This is an epidemic people are not talking about enough, and it leads to people taking unnecessary risks.”

Health officials first became aware of the problem in December, when several people reported having HIV or syphilis symptoms. Those who tested positive for either STI were interviewed to find out about their sexual partners and get them tested.

While some people were open about their sexual histories, others weren’t. Still, this cluster was identified because these people were all in contact with each other at some point over the last 12 months.

Public health experts expect the number to grow as more people get tested and are identified as part of this cluster.

Milwaukee Public School officials were quick to note that Milwaukee has a high rate of STIs, especially among people ages 15 to 24. The city leads the nation in gonorrhea infection rates and is fourth for chlamydia.

“Because schools have a significant number of students in the 15-18 age group, we are working with the Milwaukee Health Department, in a collaborative and preventive effort, to share information with young people in middle schools and high schools to keep them healthy and to protect their health,” the school district said in a statement.

In 2012, Governor Scott Walker signed an abstinence-only sex education law. While school districts are permitted to continue teaching about condoms, they have to emphasize abstinence and teach that “abstinence from sexual activity before marriage is the most effective way to prevent pregnancy and sexually transmitted diseases.”

The law also requires that a district’s curriculum for sex education classes be reviewed by a panel of “parents, teachers, school administrators, pupils, health care professionals, members of the clergy, and other residents of the school district” and allows parents to opt their children out of the classes.

Milwaukee Public Schools teach about condoms, and a demonstration of correct condom usage is included in the sex education curriculum posted online.

But the class materials don’t give the impression that condoms are very effective. They say, “Condoms have the highest failure rate of all the leading methods of birth control.”

The materials also state the condoms only prevent the transmission of HIV 85% of the time if used in a “correct and consistent” way, which is incorrect. Condoms are 97% effective if used correctly.

The materials warn teens that “most” of them will not use condoms correctly and consistently, which could give them the impression that there is no point in trying.

The class doesn’t make similar statements about abstinence, which can also be used inconsistently. Abstinence is said to be “100%” effective at several points in the materials, even though it is possible to fail at abstinence.

“Common sense suggests that in the real world, abstinence as a contraceptive method can and does fail,” said Cynthia Dailard of the Guttmacher Institute. “People who intend to remain abstinent may ‘slip’ and have sex unexpectedly.”

Last month, the director of Disease Control and Environmental Health for the City of Milwaukee Health Department Angela Hagy stressed the importance of promoting condom use.

“It is important that anyone engaging in sexual activity know how to access and use condoms correctly every time you are having sexual activity, unless you are trying to get pregnant,” Hagy said. “As a community, we must start a conversation about condom use and reduce the stigma around STI testing and awareness.”