Epidemiology of SARS-CoV-2 Infection in Mexico and Latin America

Abstract

This chapter presents some insights into COVID-19 in children. We begin by summarizing the fundamental aspects of SARS-CoV-2 and COVID-19. We also cover issues about the severity of the disease and fatality and factors associated with the outcome of pediatric patients with COVID-19. Most evidence treated in this chapter comes from reports in Mexico, but a general landscape in Latin America is pictured. COVID-19 does not seem to be so severe among children. It is worth noting that those at higher risk are the children between 0 and 2 years who develop pneumonia. In this chapter, we did not discuss extensively the Multisystem Inflammatory Syndrome nor the social impact that the COVID-19 pandemic has had on children. Many studies used for this chapter relied on open data sources resulting from a surveillance system designed for the general population. Therefore, specific variables for children were not analyzed.

1. Introduction

In November-December 2019, several cases of pneumonia of an unknown origin were reported in Wuhan, China, and the World Health Organization (WHO) declared a public health emergency of international concern [1].

From then until October 2022, the outbreak spread to 237 countries, with 626,565,321 confirmed cases, of which 6,566,037 died [2].

The Pan American Health Organization (PAHO) [3] reported on November 5, 2022, the confirmed cases, of all ages, in the Americas region (Table 1).

Region	Confirmed cases	Deaths	Case Fatality Ratio
North America	107,924,403	1,439,525	1.33
Central America	4013, 243	53,616	13.30
South America	64,184,548	1,329,987	0.20
Caribbean and Atlantic Ocean Islands	4,239,152	35,327	0.83
Null	10,869,300	219,088	2.02
Total	191,230,646	3,077,543	1.61

Table 1.

Distribution of confirmed cases, deaths, and Case Fatality Ratio for COVID-19 by area of America.

Source: Pan American Health Organization [3].

In Mexico, until 31 October, 2022, 7,111,119 confirmed cases had been reported, and from them, 330,393 had been reported dead, with a Case Fatality Ratio (CFR) of 4.65% [2].

Since the beginning of the pandemic, it was reported that the highest frequency of cases and case fatalities were in men aged 45 years and older [4]. The affectation in children under 18 years of age was lower than in the general population, and the form of COVID-19 was less severe [5].

In China, Dong et al. [5] reported 728 confirmed cases, mostly men, with a median of 7 years. Approximately 90% of the cases were asymptomatic, mild, or moderate.

2. SARS-CoV-2

Two new coronaviruses emerged and induced severe illnesses during the last 20 years. One of them is the severe respiratory syndrome coronavirus (SARS-CoV-1). It appeared in 2002 in Guangdong, China, and spread to 29 countries, with 8098 confirmed cases and 774 deaths, with a CFR of 9.6% [6, 7], and 135 reported pediatric cases (1.7% of cases) with no deaths [8].

In 2012, Middle East Respiratory Syndrome Coronavirus (MERS-CoV) emerged in Saudi Arabia, resulting in 2494 cases with 858 deaths in 27 countries, with a CFR of 34.4% [9].

Coronaviruses belong to the Coronaviridae family in the Nidovirales order [10]. In nature, four coronavirus subfamilies have been identified: alpha, beta, gamma, and delta. Alpha and beta coronaviruses apparently develop in mammals—specifically in bats—while gamma and delta have been found in pigs and poultry [10]. Corona represents the crown-like spikes on the outer surface of the virus; thus, it was named a coronavirus, which is small (65—125 nm in diameter) and contains a genome (RNA) that varies between 26 kb and 32 kb [11].

The SARS-CoV-2 was identified and characterized by Zhu et al. [12]. It uses the same cell entry receptor—Angiotensin-Converting Enzyme.

2 (ACE-2)—as SARS-CoV, highly expressed in airway epithelial cells and in other organism cells [8]. Also, Zhu et al. [8] reported the cytopathic effects and morphology. It is a member of a family of coronaviruses that infect humans. This virus grows more in human airway epithelial cells than tissue culture cells, suggesting the potential for increased infectivity in the respiratory tract.

The glycosylated spike (S) protein of SARS-CoV-2 has a 10-fold greater affinity to bind to ACE-2 than SARS-CoV-1 [13, 14].

Initially, transmission occurred from an intermediate zoonotic host to humans and later by effective human-to-human [15]. The primary transmission route is through respiratory droplets when a sick person coughs, sneezes, or speaks [16].

There are no reports of transmission of the infection through transfusions or organ transplants [17].

3. Coronavirus disease (COVID-19)

Cui et al. [18] reported in a meta-analysis that 17% of COVID-19 cases were in children less than 1 year, 24% between 1 and 5 years, 20% between 6 and 10 years, 20% between 11 and 15 years, and 18% from 15 or more years. 55% of the sample was male. Regarding the severity of COVID-19, 20% were asymptomatic, 33% mild, 51% moderate, and 7% severe, and they did not report any deaths [18]. Table 2 shows the predominant clinical data according to Cui et al. [18].

Clinical data	%	CI95%
Fever	51	45–57
Cough	41	35–47
Sore throat	16	7–25
Tachycardia	12	3–21
Rhinorrhea	14	8–19
Nasal congestion	17	6–27
Tachypnea	9	4–14
Diarrhea	8	6–11
Vomiting	7	5–10
Myalgia or fatigue	12	7–17
Hypoxemia	3	1–4
Chest pain	3	0–5

Table 2.

Distribution of clinical data in children under 18 years old.

CI95% Confidence Interval 95%.

Source: Cui et al. [18].

Dyspnea has been reported in 13% of the cases [19], and other reports have mentioned headaches and chills (both in approximately 28%) [8].

Not testing widely in many countries made it difficult to quantify the burden of SARS-CoV-2 infection in children [17].

In Mexico, the subjects who meet an operational definition undergo a COVID-19 test (RT-PCR or antigen detection). A suspected case of viral respiratory disease is anyone with cough, fever, dyspnea (severe), or headache, having at least one of the following: myalgias, arthralgias, odynophagia, chills, chest pain, rhinorrhea, anosmia, dysgeusia, or conjunctivitis. In children under five years, irritability is interchangeable with headache [20, 21].

4. COVID-19 severity

One limitation in Mexico and other countries was that RT-PCR was performed only for symptomatic patients. It led to underestimating the burden of the pandemic and underreporting of children with mild or asymptomatic COVID-19 [17]. In a joint WHO-China work, it was reported that of 55,924 confirmed cases, 2.4% were in children under 19 years of age, and of them, 2.5% developed severe disease and 0.2% critical illness [22].

In China, when studying 728 pediatric patients with confirmed COVID-19, 12.9% presented asymptomatic symptoms, 43.1% mild, 40.9% moderate, 2.5% severe, and 0.4% critical [5]. In Italy, 1.2% of the COVID-19 cases were in children under 18 years of age, and no deaths were reported [23]. In the USA, 1.7% of the cases were in children under 18 years of age [19]. In Spain, only 0.8% of the cases were in children under 18 years of age [24].

Multisystem Inflammatory Syndrome (MIS-C) was reported as related to COVID-19 and is associated with Unit Intensive Care admissions and death [25, 26]. In Latin American children, the age where the MIS-C occurred most frequently was over 10 years (35.8%) [27].

There are features in common between MIS-C and Kawasaki disease [28]. In Europe, a thirty-fold increase in the incidence of Kawasaki disease has been reported [25]. Nevertheless, a more severe Kawasaki disease was reported in children older than 5 years and was called atypical Kawasaki disease [29]. In Latin America, up to August 2020, 95 cases of MIS-C in children were reported; 54.7% were men, 11 had a pre-existing medical condition before MIS-C, 21% were admitted to intensive care, and two died [27].

5. Pneumonia

Pneumonia is considered a leading cause of death in COVID-19 patients of any age.

The development of pneumonia was the chief risk factor for mortality, with a risk of 6.45%. For those who required intubation, it increased to 8.75% [30].

In Mexico, up to May 2020, of 1443 children with COVID-19, 9.8% had pneumonia [30]. Among 141 children with pneumonia and COVID-19, the higher effect was in children under 1 year (OR = 5.83 CI95% 3.56–9.54). The male sex manifested itself as a weak protective factor for developing pneumonia (OR = 0.73 CI95% 0.51–1.04); diabetes showed a strong effect (OR = 12.61 CI95% 4.62–34.41), and the same happened with immunosuppression (OR = 7.35 CI95% 3.97–13.61) [31]. Antúnez-Montes et al. [27] also found a statistically significant relation between pneumonia and pediatric ICU admission.

6. Fatality of cases

In Mexico, until May 2020, the CFR was 0.23% for those between 0 and 5 years and 0.06% for those between 6 and 11 years [32].

Navarro et al. [33] reported that of 48,505 confirmed cases up to December 31, 2020, the CFR was the highest for children between 0 and 2 years of age (3.99), the highest among the Mexican child population. For pneumonia, the CFR was 15.46%, but the OR was 63.90%, showing the strong effect of pneumonia on mortality in Mexican children.

Confirmed cases of SARS-CoV-2 infection and deaths, in Latin America, in children under 19 years are reported in Table 3, up to May 2020.

Country	Confirmed cases in less than 19 years old		Deaths in less than 19 years old
	n	%	n	%
Argentina	1003	1.2	0	0.00
Bolivia	446	11.6	ND	ND
Brazil	4019	3.4	94	0.24
Chile	4348	9.4	0	0.00
Colombia	2087	11.8	6	0.95
Costa Rica	55	6.1	0	0.00
Cuba	238	12.5	0	0.00
Ecuador	490	1.4	6	0.21
El Salvador	102	6.4	1	3.13
Guatemala	278	12.2	ND	ND
Haiti	44	7.3	2	9.09
Honduras	204	7.2	0	0.00
Mexico	1376	2.4	9	0.15
Panama	830	8.4	ND	ND
Paraguay	184	22.0	ND	ND
Peru	4350	4.7	17	0.64
Dominican Republic	544	5.9	4	1.51
Uruguay	14	1.9	ND	ND
Venezuela	145	17.5	ND	ND

Table 3.

Distribution of confirmed cases of COVID-19 and deaths from this cause in Latin American countries.

Source: Taken and modified from [34].

Case fatality ranged from 0 to 9.09%. The countries with recorded deaths were Brazil, Colombia, Ecuador, El Salvador, Haiti, Mexico, Peru, and the Dominican Republic. These cases might have had some underlying comorbidity. For children, mortality is infrequent, and those admitted to intensive care units usually have a chronic or preexisting condition [27, 34].

As reported, case fatality is lower among children (0.39%) than in later ages (99.61%) [35].

7. Sex

In a report from China of SARS-CoV-2 infection confirmed cases, men predominated with 57.4% [5]. Among 50 children from India with co-signed SARS-CoV-2, 64% were males [36].

Up to May 2020, in Mexico, 48% of the children with COVID-19 were males, and 44.4% of those who died were men [30]. Moreno-Noguez M et al. [31] report similar results on close dates.

In Mexico, until December 31, 2020, among 48,505 confirmed cases of COVID-19, males (50.43%) and females (49.57%), the CFR was 96% for males and 0.80% for females under 18 years of age [33].

It is important to note that these reports are from the same public database of the Mexican government at different times, and there is not much difference in the results.

8. Age

Dong et al. [5] reported that among 728 confirmed cases of infection by SARS-CoV-2, 24.7% were 11—15 years old, followed by 6—10 years old (23.4%).

In Mexico, the CFR was 3.99% in children under 2 years and 0.45% in those between 12 and 17 years of age [33].

9. Comorbidities

Navarro et al. [33] report that comorbidities representing a risk of dying in adults do not have this role in the pediatric population. Tsankov et al. [37] report in a meta-analysis that comorbidities increase the risk of severe COVID-19 and mortality in children. Nevertheless, studies in the meta-analysis only included one Latin American population.

10. Conclusions

SARS-CoV-2 is a coronavirus that emerged in late 2019. Its associated disease, COVID-19, spread to almost all the world. COVID-19 seems to be mild in children. Up to May 2020, infections by SARS-CoV-2 were scarce among children in Latin America, and so were the deaths by COVID-19. The children at higher risk are those between 0 and 2 years. Most deaths were among the ones with pneumonia. Comorbidities commonly associated with poor outcomes in adults did not play a crucial role in children. The societal impact of COVID-19 on children was not treated in this chapter.

Conflict of interest

The authors declare no conflict of interest.