A young child in California has died of respiratory syncytial virus, or RSV, health officials said.
In a release Tuesday, Riverside University Health System – Public Health did not disclose the child's name, city of residence or sex, just that they were under age 4.
Additionally, officials did not reveal details about the child's illness aside from the fact that they died at a local hospital "after contracting a respiratory illness that is possibly linked to Respiratory Syncytial Virus."
Jose Arballo Jr., spokesman for RUHS – Public Health, told ABC News the death occurred late last week but was only officially released to the public on Tuesday.
He added that the child was experiencing "several days of symptoms" before being brought to the hospital and was only hospitalized for "a short period of time" before they died.
"The loss of a child is devastating and all of Public Health sends its heartfelt condolences to the family, loved ones and anyone impacted by this tragic event," Dr. Geoffrey Leung, public health officer for Riverside County, said in a statement.
The death comes as infections of RSV continue to spread across the country. Public health officials have said the season has started much earlier than usual, with autumn cases on par with those usually seen in January or February.
According to data from the Centers for Disease Control and Prevention, weekly RSV cases nationwide have risen from 5,872 the week ending Oct. 1 to 16,512 the week ending Nov. 5.
In California, the five-week average of positive RSV tests has increased from 353.3 the week ending Oct. 1 to 1,335 the week ending Nov. 5, CDC data shows.
The surge has led to several hospitals operating at or near capacity and emergency departments with long wait times.
Health experts have said RSV is emerging earlier and affecting more children than typical because of the COVID-19 pandemic.
During the pandemic, there was little to no RSV activity due to lockdowns, school closures and mitigation measures such as mask wearing and social distancing. Now, with most of these measures lifted, children are being exposed to viruses like RSV for the first time.
"That just leaves a lot of children, young children in particular, that have been born since March of 2020 who haven't yet encountered RSV infections," Dr. Larry Kociolek, medical director of Lurie Children's Hospital in Chicago, told ABC News in a recent interview. "And so that will increase the ability of the virus to spread and increase the number of children who will get infected."
Although deaths are not common and usually occur among those with pre-existing conditions, between 100 and 500 pediatric deaths are attributed to RSV every year, according to the CDC.
This is not the first reported death from RSV in the U.S. Earlier this month, California reported a pediatric death from a combination of RSV and the flu with deaths also reported in Michigan and Oklahoma.
Arballo Jr. said the county is also investigating the death of a child under the age of 10 who tested positive for RSV.
The county is asking families over the holiday season to be very careful around babies and young children, who are particularly susceptible to RSV. Arballo Jr. said adults should consider wearing a face mask and frequent hand washing, and advised against handling children if ill.