During the first months of 2021, COVID-19 case counts in the United States steadily declined-a trend attributed to the successful rollout of newly developed vaccines to tens of millions of adults. By late spring, however, COVID-19 numbers were again on the rise, with pediatric cases increasing exponentially. By September, children infected with SARS-CoV-2, the virus that causes COVID-19, had increased from about 38,000 new diagnoses a week in late July to nearly 243,000 cases.

COVID-19 infection in infants and children typically presents as mild illness. A small number of children develop severe disease, requiring hospitalization, but deaths are rare. As of last winter, the average rate of pediatric deaths from COVID-19 in the United States, United Kingdom, Italy, Germany, Spain, France, and South Korea was 0.17 deaths per 100,000 children, according to a study published in the May Lancet Child and Adolescent Health.

More recently, British researchers analyzed the data for schoolchildren ages five to 17 who tested positive for COVID-19 from September 2020 through February 2021. The data came from the COVID Symptom Study, a smartphone app-based epidemiological study in the United Kingdom that enables people to contribute their personal experience with COVID-19 symptoms and testing (parents enter data for children under age 18). The researchers found that COVID-19 lasted a median of five days in younger children (ages five to 11 years) and seven days in older children (ages 12 to 17 years). By comparison, the median duration of COVID-19 illness in adults is 11 days.

The most common symptoms in children were headache and fatigue. The next most common symptoms in younger children were (in order of frequency) fever, sore throat, abdominal pain, and persistent cough, and in older children, sore throat, anosmia, fever, and persistent cough. After a new question about nasal symptoms was added to the online questionnaire in November 2020, rhinorrhea and sneezing were also noted to be common.

So-called long COVID, defined by the researchers as cases in which symptoms persisted for at least four or eight weeks, was found to occur less frequently in children than in adults. Another analysis of COVID Symptom Study data found that 13.3% of adults had COVID-19 symptoms for at least four weeks and 4.5% for at least eight weeks. In the study by Molteni and colleagues, 4.4% of children experienced at least four weeks of symptoms while 1.8% were symptomatic for at least eight weeks, although this latter percentage may reflect a drop-off in the number of parents logging their children's symptoms past four weeks.

The now prevalent Delta variant of COVID-19 does not appear to cause more severe illness in children. According to the Centers for Disease Control and Prevention (CDC) COVID Data Tracker for COVID variants (https://covid.cdc.gov/covid-data-tracker/#variant-proportions), from mid-June to mid-August, cases of the Delta variant rose from 25% to virtually 100% of all U.S. cases. Reports of severe pediatric disease in unvaccinated "hot spots" may not stem from the Delta variant itself, researchers say, but from repeat exposures, resulting in higher concentrations of inhaled virus.

COVID-19 outbreaks described at the start of the 2021-2022 school year make clear that infected and unmasked teachers and students can cause rapid spread of the virus. A study of one such outbreak by the CDC found that a teacher in Marin County, California, who was symptomatic and intermittently unmasked in the classroom, was responsible for 27 infections in students, parents, siblings, and school. Because both long COVID and the rare but dangerous complication known as multisystem inflammatory syndrome are possible sequelae of COVID-19 in children, nurses should take a thorough history of symptoms in children (and, as applicable, of COVID vaccination), and continue to emphasize mask use, frequent handwashing, physical distancing, and isolation of those with symptoms.-Betsy Todd, MPH, RN