The tragic chain of events began in February, when people still took traditional family gatherings full of kisses, tears and hugs for granted.

And it started with one person, in Chicago. A so-called “super-spreader.” That person went to a dinner. Then a funeral. Then a birthday party.

All the while, the coronavirus spread, moving from that first “index patient” to 15 others, killing three people in the end – one of whom shared take-out food with the “super-spreader.”

The two others who eventually died were at the birthday party.

Now, that “cluster” of coronavirus cases here is the subject of a report released Wednesday by the Centers for Disease Control and Prevention. It stresses the need for social distancing to stop the spread of the virus, even within families. It points to a series of gatherings that all occurred “before major social distancing policies were implemented,” each attended by a common patient who experienced only mild symptoms.

“Super-spreading events have played a significant role in transmission of other recently emerged coronaviruses,” the report said.

The patients in the cluster ranged in age from 5 to 86 years old, according to the report. The three who died were all older than 60 and had at least one underlying cardiovascular or respiratory medical condition.

The report is a stark reminder of how the coronavirus can quickly spread through innocent gatherings. Three people believed to have been infected by the “super-spreader” at the birthday party might have then passed COVID-19 on days later to another person at church, with the passing of an offering plate.

But the report acknowledges some shortcomings in the study. Nine of the 16 patients it mentioned had “probable” cases of coronavirus. Because of the lack of lab testing, it’s possible those patients could have had an unrelated illness.

Second, data that could confirm linkages to the index patient were not available. For example, the person thought to have caught the coronavirus at church was also a health care worker and could have caught the virus elsewhere, though that person did not see any patients known to have the virus.

That said, the report also notes that “not every confirmed or probable case related to this cluster might have been detected,” meaning “the size of this cluster might be underestimated.”

Dr. Jennifer Layden, deputy commissioner and chief medical officer of the city’s Department of Public Health, said the purpose of the investigation was to “one, identify where they potentially could have been exposed and two, to try to intervene to identify contact to ensure they have the right messaging so it’s a common public health practice that we implement.”

“One of the takeaways is not so much the concept of a super-spreader, but really focusing on the importance of social distancing and social mitigation steps that have been put in place,” Layden said. “The spread among non-household members really illustrates how close contact, especially in contained spaces can lead to transmission when you get a bunch of people together, that are all susceptible.”

The index patient was tested later as part of the CDC investigation — Layden said the decision to test the index patient could be related to the level of severity of that person’s symptoms at the time.

The chain began in February after the death of someone who had died for reasons unrelated to the coronavirus, according to the report. The index patient, who had recently traveled out of state and had mild respiratory symptoms, shared a take-out meal from common serving dishes with two members of the deceased’s family the night before the funeral.

The meal lasted three hours. The funeral the next day, featuring a “potluck-style” meal, lasted two hours. During the funeral, the index patient embraced members of the deceased’s family.

Within four days, the two people who had shared a take-out meal with the index patient had developed confirmed coronavirus symptoms. One of them, identified as “patient B2.1,” would be hospitalized and died 27 days after the take-out meal. The second was managed as an outpatient and recovered. That was also the case for a third member of the family, who developed probable symptoms after embracing the index patient at the funeral.

A fourth member of the family also visited and embraced “patient B2.1” at “the acute medical inpatient ward” before that patient’s death and wore no personal protective equipment during the visit, according to the report. That person had also embraced the index patient at the funeral. Three days after visiting the patient who would eventually die, the fourth family member also developed “signs and symptoms consistent with COVID-19, including a fever and cough.”

Then, three days after the funeral, the index patient went to a three-hour birthday party, embracing and sharing food with nine family members. Three of those family members developed confirmed cases of coronavirus. Two of them were hospitalized and died.

Two people who cared for one of those two patients without personal protective equipment would also develop probable coronavirus cases. One of them likely passed it on to yet another family member, according to the CDC.

The third person with a confirmed case of coronavirus from the birthday party had a mild cough and a low-grade fever. A similar experience was reported for four additional family members who developed “probable” coronavirus cases after the party.

Three of those “probable” patients then went to church six days after first developing symptoms, according to the report. That’s where they passed the offering plate and sat for 90 minutes within one row of the health care worker, who later developed a confirmed case of coronavirus.

“Overall, these findings highlight the importance of adhering to current social distancing recommendations, including guidance to avoid any gatherings with persons from multiple households and following state or local stay-at-home orders,” the report said.

Public health officials warned against focusing on the “super-spreader” label.

“That’s not the point or the main finding at all in this article,” Dr. Allison Arwady, the head of the city’s Department of Public Health, said. “It really highlights that really innocuous activities like a child’s birthday party or really attending a funeral or sitting next to each other in church, I mean some of these sorts of things can play into significant spread ...”