The coronavirus has not hit children as hard as adults, preliminary data from the United States suggests, supporting earlier reports of what appears to be a mysterious saving grace of the deepening pandemic.

In its first report analyzing the virus’s effect on American children, the Centers for Disease Control and Prevention found that pediatric cases accounted for just under 2 percent of confirmed U.S. cases. Its research also suggested that patients younger than 18 developed fevers or coughs less often than older counterparts and were less likely to require hospitalization, although serious illness has occurred in some children.

The CDC said its findings seemed to support an earlier study on pediatric cases in China, which found that covid-19, the disease caused by the novel coronavirus, might be less severe in children. The CDC researchers cautioned, however, that the information was incomplete and that severe cases have been reported among some people younger than 18, including three deaths that remain under investigation.

“Although most cases reported among children to date have not been severe,” the CDC report said, “clinicians should maintain a high index of suspicion for covid-19 infection in children and monitor for progression of illness, particularly among infants and children with underlying conditions.”

The coronavirus’s less-severe manifestations in children have been an enduring mystery. Solving it could lead major progress in understanding how and why the virus sickens and kills those in other age groups, scientists say.

The CDC study analyzed 149,082 cases reported to the CDC from all 50 states, the District of Columbia, New York City and four U.S. territories between Feb. 12 and April 2. Of those, 2,752, or 1.7 percent, involved children younger than 18, while 113,985 involved adults ages 18 to 64. (Those over 64 were left out of the analysis because the illness is more severe for people in that age group, the report said.) Infants accounted for 15 percent of pediatric cases but were underrepresented among cases in patients of all ages.

The CDC received its first report of a case involving a child on March 2. Since March 5, it said, pediatric cases have been reported daily. Among the 2,752 pediatric cases, the median age was 11. Nearly a third of those cases involved children ages 15 to 17; 27 percent were among those ages 10 to 14; 15 percent were among those ages 5 to 9; 11 percent were among those ages 1 to 4; and 15 percent were among those under 1.

Data on symptoms, underlying conditions and hospitalization status was available in only a small proportion of cases, meaning that the results “must be interpreted with caution,” the report warned.

In the 291 pediatric cases for which data was available, 73 percent had a fever, cough and shortness of breath. That number was significantly higher among the 10,944 adult cases for which data was available, at 93 percent. Other symptoms, including muscle pain, sore throat, headache, nausea/vomiting, abdominal pain and diarrhea, were more commonly reported in adults. Runny noses, meanwhile, were slightly more prevalent among children.

In the 745 pediatric cases for which hospitalization status was available, 147 were hospitalized and 15 admitted to intensive care. That number represents a hospitalization rate of 5.7 to 20 percent and an ICU admission rate of .58 to 2 percent. By comparison, the study said, 10 to 33 percent of infected adults were hospitalized and 1.4 to 4.5 percent placed under intensive care.

“Three deaths were reported among the pediatric cases included in this analysis; however, review of these cases is ongoing to confirm covid-19 as the likely cause of death,” the study said.

It noted that the findings were “largely consistent” with the report out of China, which found that 41.5 percent of 1,391 pediatric patients had fever, 48.5 percent had a cough and 1.8 percent were admitted to an ICU.

A later study of 2,143 pediatric cases in China suggested that the infection might be more severe among infants. Released last month in the journal Pediatrics, it found seven infants and two preschoolers between the ages of 1 and 5 whose conditions were considered critical. Another 33 infants and 34 children between 1 and 5 years old developed severe illness. The researchers wrote in the study that their findings suggested that “young children, particularly infants, were vulnerable.”

In its new report, the CDC found that infants made up 59 of the 147 pediatric hospitalizations and five of the 15 pediatric ICU admissions, but it noted that “most reported U.S. cases in infants had unknown hospitalization status.”

“More systematic and detailed collection of underlying condition data among pediatric patients would be helpful to understand which children might be at highest risk for severe covid-19 illness,” the report said.

Although most cases reported among children have not been severe, the CDC stressed that those with mild symptoms or asymptomatic cases are likely playing a part in the spread of the virus, which had infected 362, 170 people and killed 10,752 in the United States as of Monday.

Because of that, the report said, social distancing and everyday preventive actions continue to be “recommended for persons of all ages.”