A man from an ultra-Orthodox Jewish community in Brooklyn, New York, traveled to Michigan without knowing he was infected with measles — a highly contagious respiratory infection that has infected more than 500 people in the U.S. so far this year.

The man, who has not been identified and has since been dubbed “Patient Zero,” recently traveled to Detroit to raise money for a charity in the Brooklyn community, The Washington Post first reported. Though he felt ill and saw a doctor once he arrived in Detroit (he reportedly drove through the night to reach the destination), his fever and cough were initially diagnosed as bronchitis.

In the weeks that followed, the man, who traveled from Israel to Brooklyn in November before heading to Detroit in March, unknowingly spread measles to at least 39 people. Nearly all the cases were reported in those who live in the Detroit suburb of Oakland County, where the man spent the majority of his time.

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At one point, the man reportedly called the doctor again after he developed a rash, a key symptom of measles. But it was allegedly dismissed as an allergic reaction.

But the doctor, who has also not been identified at this time, later began to worry the man may have contracted something more severe. He called the health department and left a voicemail that contained the man’s phone number. Health department officials, however, were unable to reach the man, as there was “a problem with his cellphone,” per The Washington Post.

Eventually, the man was located, thanks to the help of Jewish community members and Steve McGraw, who heads the Oakland emergency medical services.

“There is only one disease, and you have it,” McGraw told the man when he was located, he recalled to the newspaper. “He put his head down and was very emotional. I could tell from the look on his face that he was devastated.”

“He was doing the math in his head” to determine how many people he had come into contact with during his trip, McGraw described. “This guy was walking around all over the community and contagious. We knew we had a really significant exposure," he added.

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The man visited some 30 locations in about a week’s time and likely had contact with “hundreds” of members of the local ultra-Orthodox community.

“Every one of our cases has had a link to the initial case,” Leigh-Anne Stafford, health officer for Oakland County, told The Washington Post. A blood test later confirmed the man had measles.

The strain the man contracted "had an epidemiologic link to an ongoing outbreak of measles in Brooklyn, New York," Lynn Sutfin, a public information officer with the Michigan Department of Health and Human Services, told Fox News in an email Wednesday.

"The additional cases have an epidemiologic link to the [man's] case or exposure locations," she added.

Following the man’s official diagnosis, Oakland County health officials said they’ve vaccinated more than 2,000 people in the ultra-Orthodox community against the measles.

The Centers for Disease Control and Prevention (CDC) said Monday 555 measles cases have been confirmed so far this year, up from 465 as of a week ago.

While 20 states have reported cases, New York has been the epicenter. Nearly two-thirds of all cases have been in New York, and 85 percent of the latest week's cases came from the state. Most of the New York cases have been unvaccinated people in Orthodox Jewish communities.

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The 2019 tally is already the most since 2014 when 667 were reported. The most before that was 963 cases in 1994.

The CDC recommends that all children get two doses of measles vaccine, which is 97 percent effective.

Other states reporting measles cases this year include Arizona, California, Colorado, Florida, Georgia, Illinois, Indiana, Kentucky, Maryland, Massachusetts, Michigan, Missouri, Nevada, New Hampshire, New Jersey, Oregon, Texas and Washington. After the CDC issued its report Monday morning, Iowa officials said they, too, had seen a case.

The Associated Press contributed to this report.