Analysis of Hospital Lethality of COVID-19 in Mexico

1Division of Health Sciences, Campus Leon, Universidad de Guanajuato. Leon, México; C.P. 37670. 2Department of Medicine and Nutrition, Division of Health Sciences, Campus Leon, University of Guanajuato, León, México C.P. 37670. 3Department of Statistics, General Directorate of Planning and Development, Institute of Public Health of the State of Guanajuato, Guanajuato, Mexico C.P. 36250. 4Department of Research and Technological Development, Directorate of Teaching and Research, Institute of Public Health from Guanajuato State, Guanajuato, Mexico C.P. 36250. 5Directorate of Health Services, Institute of Public Health from Guanajuato State, Guanajuato, Guanajuato, Mexico C. P. 36000. *Corresponding Author E-mail: npadillar@guanajuato.gob.mx

In December 2019, in Wuhan, China, there were alerts about cases of pneumonia of unknown etiology 1 . On February 11, 2020, the World Health Organization (WHO) named its causative agent Coronavirus disease 2019 (COVID-19), while the International Committee on Taxonomy of Viruses (ICTV) named it a type of severe acute respiratory syndrome virus. -2 (SARS-CoV-2) 2 . The WHO declared it a pandemic in March 2020 3 . The first case of COVID-19 in Mexico was confirmed on February 28, 2020. As of June 25, 2021, 2,684,128 cases of COVID-19 had been confirmed with 244,830 deaths 4,5 .
SARS-CoV-2 is a single-stranded RNA virus. It belongs to the Coronaviridae family and is a beta Coronavirus 6 . Inhalation of respiratory droplets and aerosols is the main route of transmission 7 . It has an incubation period of 1 to 14 days, where the clinical manifestations usually appear between the third and seventh day with typical signs and symptoms such as sore throat, fever, cough, fatigue, myalgias, nasal congestion, and runny, anosmia, difficulty in breathing 8 . There are also atypical complaints such as diarrhea, nausea, and vomiting 9,10 .
80% of SARS-CoV-2 cases resolve without requiring hospitalization, 15% require hospitalization, 5% require intensive therapy and support with invasive mechanical ventilation. Therefore, these last two scenarios present a severe condition due to COVID-19 11 . Being a man, having an advanced age and comorbidities such as diabetes mellitus, high blood pressure, obesity, cancer, and chronic kidney disease, predisposes to a severe COVID-19 due to SARS-CoV-2 8,12 .

Hospital fatality
The number of patients infected by COVID-19 is underestimated. Some of the reasons are that besides the impossibility to carry out an adequate number of tests for its detection, asymptomatic patients, and those with mild symptoms or with scarce access to health services do not attend to medical revision 13,14 . The Secretary of Health of the United Mexican States established guidelines to regulate the conduct of its health care staff during the contingency due to SARS-CoV-2 and has studied the impact of this disease by quantifying the number of confirmed cases and the observed mortality. Nevertheless, the lack of identification of patients infected by COVID-19 causes bias when calculating mortality, showing an unreliable picture to analyze the severity of this pandemic 15,16 .
Hospitalized patients present a more severe disease due to this infection. Therefore, knowing how many of those hospitalized died (that is, knowing the hospital fatality) offers the possibility of identifying the severity of this pandemic more realistically. It is known that lethality is not synonymous with mortality; the first quantifies the severity of a disease, and the second measures the number of deaths that occurred in a determined population 17 .
The coding of the International Classification of Diseases (ICD-10) has allowed the registration of patients from COVID-19 care centers in national platforms for easy monitoring of the pandemic. In this way, the ICD-10 code U071 is designated to cases of COVID-19 confirmed with a positive laboratory result. On the other hand, patients with suspected SARS-CoV-2 infection that meet clinical and epidemiological criteria, with proof of inconclusive or unavailable laboratory, are given the ICD-10 code U072 [18]. Thanks to national platforms, it is possible to calculate the hospital fatality rate of COVID-19 through its ICD-10 code since they allow to know the number of infected who required hospitalization and the number of deaths from this cause.
Institutions and countries have studied the behavior of the SARS-CoV-2 pandemic based on lethality. According to the WHO, the fatality rate for this disease ranges from 0.00% to 1.63% 19 . The Pan American Health Organization estimated that Mexico had a fatality rate of 11%, becoming the country with the highest fatality rate in Latin America after the first 90 days of the pandemic 20 . Hospital fatality has also been analyzed in other countries; In France, a hospital fatality rate from COVID-19 was 0.174% 21 , in Italy, it was 29.7% 22 . In Mexico, hospital fatality, studied in patients with invasive mechanical ventilation, was 80.9% 23 .
This study aims to describe the hospital lethality of COVID-19 (or SARS-CoV-2) during 2020 in Mexican Hospitals from the Ministry of Health. For this purpose, we considered the patients registered with the condition ICD-10 U071 or ICD-10 U072.

study design
The research protocol was approved by Ethics on Research Committee from Hospital General Silao from the Institute of Public Health from Guanajuato State (ISAPEG).
A quantitative, descriptive, analytical, cross-sectional, and retrospective study was performed.
It was used the preliminary registry of the National System on Basic Information in Health from the Secretary of Health. Discharges with the principal condition CIE-10 U071 and CIE-10 U072 from 2020 were identified in the database 24 to determine the hospital lethality of COVID-19.
The variables reviewed for this study were sex, age group, discharge cause (death and non-death), and the Mexican entity of discharge. Registries with non-specified data were included.

statistical analysis
Descriptive statistics are presented for the variables of age group, sex, and Mexican entity of discharge. The Chi-Square test was used for the difference in proportions between men and women regarding the discharge cause. The hospital fatality rate of COVID-19 was calculated for overall registries, sex, discharge status, and age groups. For comparing the expected and observed lethality, and among females and males, z tests for proportions were performed.
The alpha value was set at 0.05 to assess statistical significance. The statistical analysis was performed in STATA 13.0' ® (Stata Corp., College Station, TX, USA).

results and discussion
The number of registries included in the analysis was 71,189. From them, 43,786 corresponded to persons discharged for a reason distinct to death, and the remaining 27,403 due to death.
According to the chi-squared test result (p <0.05), the sex and discharge are statistically related ( Table 1).
The age at discharge was analyzed and categorized into five-year age groups. Most discharged persons were between 55-59 years (9,037, which represents 12.69% of the total number of discharges), followed by the group of 50-54 years (8,549, corresponding to 12.01%). Regarding the distribution of discharges due to death, the group of 60-64 years concentrated the highest number of registries (3,739, which represents 13.64%). The subsequent groups, in decreasing order, were the group of 55-59 years (3,614, corresponding to 13.19%); the group of 65-69 years (3,466, corresponding to 12.65%) deaths and the group of 50-54 (3,093, corresponding to 11.29%). Almost half of the discharges due to death corresponded to persons between 50 and 69 years (13,912, which equals 50.77% of the total) ( Table  2).

Hospital fatality of coVid-19 in Mexico during 2020
The hospital fatality rate was 38.49%. The hospital fatality calculated for sex was 40.75% for men and 35.03% for women. Therefore, men exceeded the general hospital lethality. Regarding the hospital fatality of COVID-19 by five-year age groups, it stands out that the age groups that range from 55 years to 99 years obtained hospital mortality from COVID-19 higher than the general one ( Table 2). A Z test was performed for the hospital fatality proportions in terms of sex, obtaining that the difference in hospital mortality proportions between men and women is statistically significant (p <0.05).
Nayarit, Tabasco, and Aguascalientes are among the three states with the lowest hospital fatality due to COVID-19. On the other hand, the Mexican states with the highest hospital fatality due to COVID-19 in 2020 were Coahuila, Puebla, and Baja California (Figure 1).
Of the 32 states of the republic, 19 exceeded the general hospital lethality of the country (38.49%). Puebla and Coahuila were the only two states where hospital lethality from COVID-19 was higher than 50% (Table 3).
Regarding the general discharges, most occurred in men, like the reported in the literature, since men have a more severe condition due to COVID-19 25, 26 . The same phenomenon is present in older ages where there is a higher possibility of aggravated symptoms and death from COVID-19, Mexico state, Mexico City, and Guanajuato concentrated the highest number of discharges, compared to Nayarit, Colima, and Aguascalientes, with the lesser discharge numbers. During the first three months of the pandemic, Mexico state and Mexico City were already listed as states with many cases with COVID-19, while Nayarit and Colima also did so as states with fewer cases 16 .
Regarding hospital lethality, Mexico surpassed countries like Italy and France with a hospital lethality of 38.49% against a lethality of 29.7% and 0.174%, respectively 21,28 . Compared to the first three months of the pandemic in Mexico, during 2020, the lethality increased from 9.67% to 38.49%. However, it continued to exceed the global lethality, which, according to the WHO, ranges from 0.00% to 1.63% 16,19 . It is verified in this and other studies that hospital mortality is higher in males and older ages 22 .
It is worth noting that states such as Nayarit, Tabasco, and Aguascalientes, have a fatality rate close to that reported by PAHO after the first three months of the pandemic in Mexico. Comparing these results with the obtained for other states, it is possible an under-registration of discharges due to COVID-19 in those states.
Despite having been two of the states with the highest number of discharges due to SARS-CoV-2, Mexico City and Guanajuato did not exceed general hospital lethality. Maybe the health structure in these two states contributed to the COVID-19 graduates receiving better care and, therefore, a more favorable outcome. In Mexico state was observed a hospital lethality rate higher than the average. Perhaps caused by high attrition of its health personnel and fatal results in graduates, something already hypothesized in the literature, where a higher number of patients was concentrated 21 .
Although Puebla and Coahuila were not among the states with the highest number of discharges, they had a high hospital fatality rate. It may be due to management deficiencies of hospitalized patients or an ineffective registry of COVID-19 cases in the other states. limitations Due to the constant actualization of the National System on Basic Information in Health from the Secretary of Health, the statistical analysis was made with preliminary data. Hence, maybe a lower number of discharges was considered, resulting in a lower hospital fatality rate than the real one.

conclusions
Besides the deaths caused directly by COVID-19 (those that occurred due to respiratory failures), many deaths were indirect in persons with comorbidities exacerbated by this disease. Access to health services, social changes derived from job loss, home protection, and changes in social dynamics, facts expressed in the general mortality excess, cannot be quantified in our study.
Undoubtedly, Mexico has a high hospital fatality rate compared to other countries. Since it is a country with a large territory divided into sovereign states, it is expected that each state has different levels of health system efficiency, and therefore to observe differences in hospital lethality due to the SARS-CoV-2 pandemic. However, there are similar patterns with other persons infected worldwide: this disease is more severe for males and older age subjects.

Conflict of Interest
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. author contributions CMC: designed the protocol, analyzed the data, and wrote the final report. ELL: participated in designing the protocol, analyzing the data, and writing the final report. CADC: reviewed the data analysis and participated in writing the final report. GFV: reviewed the data analysis and participated in writing the final report. DADM: obtained the database from dynamic cubes and participated in writing the final report. FJMV: reviewed the data extraction and participated in writing the final report. NPR: reviewed the manuscript critically and corrected it. DPS: participated in designing the protocol and analyzed the data.

Funding
No funding for this research.