Introduction

The coronavirus disease 2019 (COVID-19) pandemic caused by SARS-CoV-2 (severe acute respiratory syndrome type coronavirus 2) began in Wuhan, China, in late 2019. This disease has affected more than 6 million people and has left health and economic implications worldwide¹-³. The initial characterization was described in adults⁴, but neonatal and pediatric cases began to be identified as the epidemic progressed⁵-⁸.

Although the prevalence of COVID-19 in children represents a low percentage of all cases reported in different series or cross-sectional studies, ranging from 0.8% to 2.7%⁹-¹¹, the number of affected children and their different clinical presentation compared to adults⁴,¹² can be a challenge for pediatricians.

In children, SARS-CoV-2 affects males slightly more, as observed in adults. Fever and cough are also the most common symptoms, but with a lower prevalence than in adulthood. Findings in laboratory tests and imaging studies seem to be more variable. Disease severity is lower than in adults⁹,¹⁰,¹³-¹⁵, and mortality due to COVID-19 in children is lower than influenza and other respiratory infections¹⁶.

Despite this, the possibility of complications, intensive care requisition, and mechanical ventilation exists¹¹,¹⁷,¹⁸. In addition, a possible association between COVID-19 and a condition similar to severe Kawasaki disease called multisystem inflammatory syndrome is being studied¹⁹-²².

The objectives of this study were to describe the clinical and epidemiological characteristics of the confirmed COVID-19 pediatric cases in the state of Sinaloa, Mexico, and to describe the characteristics of the patients admitted to the Hospital Pediátrico de Sinaloa Dr. Rigoberto Aguilar Pico.

Methods

During the first 3 months of the pandemic in Sinaloa (March, April, and May 2020), clinical and epidemiological information of pediatric patients with SARS-CoV-2 infection was collected. The disease was confirmed by polymerase chain reaction (PCR) test of respiratory secretions. The patients were identified in the Sistema de Vigilancia Epidemiológica de Enfermedades Respiratorias (Epidemiological Surveillance System of Respiratory Diseases, SISVER) of the Secretaría de Salud (Ministry of Health). At the time of sampling for PCR, demographic data were obtained. These data included if patients had contact with SARS-CoV-2-positive individuals (defined as any person, household, or outside with a positive PCR confirmation test who had been in close contact with the child for more than 15 min, without wearing personal protection equipment, in the previous week), signs, and symptoms. The characteristics were extracted and recorded in a pre-established format. Patients were followed up by telephone at least 2 weeks after the date of onset of symptoms. We attempted to contact everyone twice by phone, sent a WhatsApp message, and asked for their verbal consent to participate in this study. The same format was used to record information on positive patients admitted to the Hospital Pediátrico de Sinaloa. This second-level public hospital serves as a referral center for Sinaloa and surrounding states. We also describe laboratory tests and imaging studies ordered by the treating physician.

Patients were classified according to the severity of illness based on clinical syndromes defined by the World Health Organization²³: asymptomatic, mild (upper respiratory infection), moderate (pneumonia), severe (severe pneumonia), or critical (severe acute respiratory syndrome SARS, sepsis, or septic shock) disease. Epidemiological and clinical characteristics are presented in a descriptive manner using absolute numbers and percentages, or medians and interquartile ranges. The analysis was performed using Excel version 16.37.

Results

Between March 1 and May 31, 2020, 3434 SARS-CoV-2 positive cases were confirmed in the state of Sinaloa: 51 (1.5%) of them were under 18 years old. Of the 51 children and adolescents, 26 were male (51%), and the median age was 10 years (interquartile range 11). A positive contact was identified in 33 children.

The most frequent symptoms were fever (78%), cough (67%), headache or irritability (57%), odynophagia (20%), and rhinorrhea (20%). Vomiting and diarrhea were reported in 10 and 14%, respectively (Table 1). Three children were identified with cancer, one with chronic kidney disease and hypertension, three with obesity, one with a lung abscess and sequelae from a head injury.

We contacted 37 patients to verify their clinical evolution and classify them according to the severity of the disease. Seven children were asymptomatic (19%), 23 with mild (62%), three with moderate (8%), one with severe (3%), and three with critical (8%) disease (Table 2). Asymptomatic children were identified by contact tracing when any of their relatives were positive. Three deaths were reported in three children with comorbidities: a 4-month-old male with Down syndrome, congenital heart disease, and hypothyroidism; an 11-year-old male with chronic kidney disease and hypertension; and a 14-year-old male with sequelae from head injury who suffered a concomitant lung abscess. These patients showed a progression of respiratory disease. No thrombotic phenomena or severe vasculitis were identified.

The characteristics of ten children admitted to the Hospital Pediátrico de Sinaloa are described in Table 3. The reasons for admission were diverse. In four patients, COVID-19 was suspected since admission (patients 5, 6, 8, and 10). The other six patients were admitted for different reasons. However, as they later developed fever and cough, SARS-CoV-2 infection was suspected. Two had been hospitalized for accidents. A patient with acute lymphoblastic leukemia (ALL) had undergone chemotherapy. Another patient was admitted for pancytopenia and de novo ALL diagnosis. One more patient was admitted because of ventriculoperitoneal valve dysfunction. Another patient diagnosed with Down syndrome, ventricular septal defect (VSD), and hypothyroidism had been hospitalized for more than 2 months. This last patient developed a critical illness and died. The other nine patients presented mild (seven) or moderate (two) disease and were discharged due to improvement. In four patients, the infection was considered to be hospital-acquired. Seven patients had normal leukocytic and lymphocytic count. Leukemia patients (three) showed leukopenia, and one patient with pertussis-like illness showed leukocytosis. A ground-glass pattern in lung tomography was demonstrated in six children; five patients had only mild disease symptoms with the upper respiratory infection symptoms.

Discussion

This case series illustrates the clinical and epidemiological characteristics of children infected with SARS-CoV-2 during the first 3 months of the pandemic in Sinaloa. The ratio of pediatric cases relative to total confirmed cases was 1.5% within the range of previous reports, which varied between 0.8% and 2.7%⁹-¹¹. We found more confirmed cases in males and adolescents and school-age children compared with young children; most of the cases were mild or moderate. The most frequent symptoms were fever, cough, and headache (or irritability). These findings are consistent with those published in other case series and systematic reviews⁹,¹⁰,¹³-¹⁵. The presence of ground-glass pattern on lung tomography in children with mild disease or asymptomatic children has also been reported²⁴-²⁶. No children that met the full criteria of the multisystem inflammatory syndrome were identified.

Differences in the clinical picture were observed among the children diagnosed at the Hospital Pediátrico de Sinaloa. Only four of the ten children were hospitalized for suspected COVID-19. The other six were admitted for different reasons. However, they later developed a fever and were identified as infected with COVID-19. The RT-PCR (reverse transcriptase-polymerase chain reaction) test should be performed in every patient admitted to the hospital to identify infected individuals. From a practical and economic point of view, testing every patient is not possible. On the one hand, the disease prevalence in children is lower than in adults²⁷,²⁸; on the other hand, resources are limited for many tests. Identifying seven asymptomatic children in the state series may also have implications for transmission in the community and should be considered from an epidemiological surveillance point of view.

Although most patients in this series had an asymptomatic, mild, or moderate infection, the possibility of complications is always present in children, especially those with comorbidities¹¹,¹⁷,¹⁸. All three deaths occurred in patients with other pathologies. The proportion of severe or critical children should be small; however, considering the nationwide case increase, this may represent a logistical challenge for pediatric or general hospitals. The two SARS-CoV-2 positive neonates indicate that the possibility of infection exists and should be considered in maternity hospitals, although this group’s frequency is also low. Even so, the burden of care should be less than that caused annually by the influenza virus¹⁶.

This study has limitations. First, only 70% of the cases could be contacted to corroborate the evolution and define the disease severity. Although we made an effort to include every patient by making two phone calls and sending a message through WhatsApp, we could not contact all. Second, the description of the symptoms from the moment of diagnosis is subjective. Third, laboratory tests and imaging studies results were limited to patients attending the Hospital Pediátrico de Sinaloa, which were ordered based on the attending physician’s judgment. Findings may vary for children who were not hospitalized or who were admitted to other institutions.

During the first 3 months of the pandemic, SARS-CoV-2 infection in children was mostly asymptomatic or mild in Sinaloa. The possibility of complications exists, especially in children with comorbidities. As long as outbreaks continue, pediatric cases’ epidemiologic surveillance should remain to define transmissibility in children and define public policies for returning to school.