Spanish study shows infections in children occur early in COVID-19 epidemics

By Dr. Liji Thomas, MDApr 8 2020

With the spread of COVID-19, scientists are finding out more about the disease. One major aspect that is being studied is how the virus affects children. A new report from Spain, published in the journal JAMA Pediatrics in April 2020, shows that pediatric populations are infected early in the epidemic and that about 10% of those with symptoms suggestive of infection test positive. Severe infection can also occur among children, requiring hospitalization and intensive care.

Image Credit: Alexander Lukatskiy / Shutterstock

Screening among children

The epicenter of the pandemic is now in Europe, in Spain, Italy, Germany, and the UK. The first case was reported in Spain on January 31, 2020, but the number of confirmed cases is now at almost 150,000, with a fatality rate of approximately 10%.

The study

The study was based on a registry of tested cases, to gain an idea of how many cases were confirmed among those tested, and how severe the disease was in children. The study period was between March 2, 2020, to March 16, 2020, covering 30 secondary and tertiary hospitals in Madrid, Spain. This covered only the first two weeks of the epidemic.

The children screened during this period by pediatricians at these hospitals were selected as per the guidelines of the Spanish Public Health authorities. They were typically ill and either already in hospital or likely to be admitted soon, or they had clinical features of COVID-19 with an underlying disease that raised the risk of complications.

The data was collected after verbal consent, and if results were positive, further written consent was obtained from such patients. All patients were tested by real-time polymerase chain reaction (rPCR).

The findings

The researchers found 365 children who underwent screening within the hospitals within the study period. The first week saw 6/103 patients turning up positive, that is, about 6% of screened children. This went up to 11% by the end of the second week. By March 16, 2020, there were 41 confirmed pediatric cases among the almost 4700 total cases, which accounts for about 0.8% of the cases in the region of Madrid.

By age, they found that the median age of the patients was three years, but for those who tested positive, it was one year. The initial diagnoses were upper respiratory tract infection, in 34%, fever of unknown origin in 27%, viral-like pneumonia in 15%, bronchiolitis in 12% and gut symptoms, bacterial-like pneumonia and asthma exacerbation, each in 5% or less.

Of the 41 positive cases, 25 were hospitalized, and four required pediatric intensive care unit (PICU) admission. Again, 4 needed supportive respiratory care beyond just oxygen. Only 1 of these 4 had a history of previous lung disease, in the form of repeated wheezing. Two of them also had influenza B coinfection.

What does the study show?

The researchers found that as in previous studies, the Spanish series shows the illness occurs in children below the age of 19 years in only 2% of total confirmed cases. In Madrid, children in whom the presence of COVID-19 was confirmed needed to be admitted for disease symptoms 60% of the time. In most cases, the admission was due to respiratory symptoms, namely, those which fit the Chinese definition of severe COVID-19 disease – rapid breathing, hypoxia, and oxygen saturation below 92%, or critical disease, namely, respiratory failure.

In China, the number of children with severe or critical illness among those with confirmed COVID-19 was less than 3%. In the current study, the major limitation to the reliability of the findings is the low number of children who underwent testing. Initially, testing was confined to those who had been in contact with a COVID-19 patient. As the epidemic began to spread, Madrid was declared to have community transmission on March 9, 2020.

Following this, public health authorities restricted pediatric screening to those children who were in hospital with clinical features suggestive of COVID-19, or those who had other underlying disease conditions and were at increased risk for complications.

Some children were tested without hospitalization because they were deemed to be likely to be admitted, though they were finally discharged. On the other hand, some children with only mild disease were tested, leading to a still lower degree of admissions. As a result of this policy, testing probably picked up only children with moderate to severe disease, biasing the results.

At the same time, pediatricians were arguably more aware of the diagnosis of COVID-10 at this date, and the use of different criteria to decide on the need for hospitalization and oxygen therapy, as well as possibly a variation in the host response to the infection.

The study was also limited by the low sensitivity of the tests used, since rtPCR carried out on pharyngeal and nasal swabs may return positive results in only about 30% to 60% of tests. This means that the number of children who actually were infected could have been higher than the number reported by a large percentage.

Children can be infected early in the course of a COVID-19 epidemic and should, therefore, be shielded from infection. Testing patients with symptoms similar to those of COVID-19 shows that about 11% of them have the illness. A percentage of these children may develop severe illness. This percentage was low in China, but very high in Spain, showing that more study is required to understand how this disease affects children.