(CBS) — Chicago’s top health administrators are taking aim at men who use smartphone apps to hook up with other men for sex after several cases of what authorities call invasive meningococcal disease.

Three confirmed cases have been reported among what’s called “MSM,” or men who have sex with men.

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CDPH Commissioner Dr. Julie Morita says meningococcal disease refers to any illness caused by the bacteria and can include meningitis and bloodstream infections.

She says people who need to get the vaccine are MSM who are HIV positive, MSM who use the online hookup apps, and MSM who have anonymous sex.

Morita also says CDPH is working with some of the popular apps to get the word out.

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They hope to issue some kind of warning that reminds users to exercise caution and get vaccinated.

The disease spreads through close contact with saliva, that can include kissing, sexual contact, sharing drinks or using the same cigarette.

David Ernesto Munar, CEO of the Howard Brown Clinic, says the alert means people should be careful about their sexual contacts.

“Those are always important messages for people to think about the risk factor and take appropriate prevention or screening if think they’ve been exposed,” said David Ernesto Munar, CEO of the Howard Brown Clinic.

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For a list of vaccine locations, click here. For more information, see the CDPH’s fact sheet or visit www.cityofchicago.org/health.