Monkeypox continues to spread. 105 Chicagoans infected as vaccines roll out, health officials say.

Since monkeypox was first detected in the city nearly a month ago, 105 Chicagoans have been diagnosed with the virus, health officials said.

The cases have mostly involved men who have sex with men, officials said. The city has begun to offer targeted vaccinations.

“I do expect that number to continue to grow,” said Chicago Public Health Commissioner Dr. Allison Arwady. Health officials are reacting quickly to the spread, and the disease “is not COVID,” she said.

The city has already received 5,409 doses of the monkeypox vaccine from the federal government, said Massimo Pacilli, the Chicago Public Health Department’s deputy commissioner of disease control. Distribution has targeted those in close physical contact with people diagnosed with monkeypox, as well as people who may be at higher risk of contracting the disease because of their sexual activity.

“There’s nothing about the virus that makes it more likely to be in men who have sex with men; it’s just that’s the close network that we’ve seen it spreading in initially,” Arwady said.

The vaccine is not currently recommended for the general public, including men who have sex with men who don’t have additional risk factors, such as having had sex in a social venue or with multiple partners, Pacilli said. Another 7,493 doses of the vaccine are expected to arrive in Chicago soon, he said.

“We are more than ready to ramp up,” Arwady said.

[ Cory Franklin and Robert A. Weinstein: Monkeypox is not our next pandemic, but it has lessons for us ]

The availability of effective testing, antiviral treatments and vaccines for the spreading virus make the early response to it different from the early response to COVID-19, said CDPH Medical Director Dr. Janna Kerins.

Monkeypox is also considerably less transmissible, Arwady said.

“It does really seem to be that very close contact. This is not passing to somebody in the grocery store,” Arwady said.

The city has begun to monitor waste water to track the virus’ spread, she said. No cases have been detected in local health care workers who have interacted with diagnosed patients, Arwady added.

Monkeypox “is not a new virus. It’s something that we’ve known about for decades,” Kerins said. The disease is endemic to parts of Africa. A past American outbreak occurred in Illinois in 2003, which was linked to prairie dogs.

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The viral illness typically begins with flu-like symptoms and swelling of the lymph nodes before progressing to a rash on the face and body. The illness typically lasts two to four weeks. According to the CDC, monkeypox cannot be spread by people who don’t have symptoms.

The CDC was reporting 866 cases in the United States as of Monday. The current outbreak is most severe in parts of western Europe, though cases have been reported across the globe.

[ In early June: Illinois announces first probable monkeypox case ]

The monkeypox virus, closely related to the smallpox virus, is easy to avoid because of its visibility, said Dr. Sharon Welbel, Cook County Health’s director of hospital epidemiology and infection control and prevention. The monkeypox rash grows to look like a large pimple and often starts on the face, she previously told the Tribune. The rash can resemble herpes, chickenpox and syphilis, she said.

Epidemiologists have also confirmed that the monkeypox version spreading in Illinois is less aggressive and associated with very low mortality rates, Welbel said.

Health officials encouraged anyone with a new or unexplained rash to call their health care provider and to avoid sex and intimacy until getting checked out.

jsheridan@chicagotribune.com

Twitter @jakesheridan_