Health officials have expressed concern over a simultaneous rise in coronavirus delta infections and cases of a respiratory virus known as respiratory syncytial virus, or RSV — a highly contagious, flulike illness that is typically more likely to affect children and older adults.

Cases of RSV have risen gradually since early June, with an even greater spike in the past month, according to data by the Centers for Disease Control and Prevention.

RSV, which can cause symptoms that include a runny nose, coughing, sneezing and fever, normally begins to spread in the fall, making this summer spike unusual.

In a series of posts on Twitter, Dr. Heather Haq, a pediatrician at Texas Children’s Hospital in Houston, described an increase in both coronavirus and RSV hospitalizations. Haq is also the chief medical officer for the Baylor College of Medicine International Pediatric AIDS Initiative at Texas Children’s Hospital.

“After many months of zero or few pediatric COVID cases, we are seeing infants, children and teens with COVID pouring back into the hospital, more and more each day,” she wrote, adding that patients have ranged in age from 2 weeks to 17 years old, including some with COVID pneumonias.

“We are on the front end of a huge COVID surge,” wrote Haq, who could not be reached for comment Sunday. “We are now having winter-level patient volumes of acutely ill infants/toddlers with RSV, and I worry that we will run out of beds and staff to handle the surge upon surge.”

RSV cases in Texas began to increase in early June and appeared to peak in the middle of July.

Florida has also experienced a similar spike in RSV cases, where infections “were above those seen at this time in past years,” according to a surveillance report of the virus.

In Louisiana, where cases have jumped by 244% in the past two weeks, Our Lady of the Lake Children’s Hospital in Baton Rouge was nearing its capacity Friday.

In Oklahoma, which also has seen a spike in RSV cases, beds are becoming scarce at hospitals.

The rise in RSV cases comes as new coronavirus infections have risen by 148% in the United States in the past two weeks and hospitalizations have increased by 73%.

The surge of coronavirus infections has been largely attributed to the highly contagious delta variant and to low vaccination rates in some states.

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This article originally appeared in The New York Times.