Risk factors for severe disease in pediatric respiratory syncytial virus infections.

OBJECTIVES: To assess factors associated with the risk of severe disease in children aged 5 years or younger with laboratory-confirmed respiratory syncytial virus (RSV) infection. STUDY DESIGN: We conducted a nationwide retrospective cohort study in Mexico. METHODS: Eligible participants included children aged 5 years or younger with laboratory-confirmed RSV infection January 1, 2023, and May 15, 2024. We collected relevant clinical and epidemiological data. Risk ratios (RR) and 95% confidence intervals (CI) were employed to identify factors associated with the risk of severe disease, characterized by clinical and radiographic evidence of bronchiolitis or pneumonia requiring hospital admission. RESULTS: Data from 2022 children were analyzed and the overall risk of severe disease was 21.0% (n = 424/2022). In multiple generalized linear regression analysis, a personal history of immunosuppression (due to any cause) showed a protective effect (RR = 0.14, 95% CI 0.05-0.42, P = 0.001) against severe RSV disease, while an increased risk was documented for each additional day elapsed between the date of symptom onset and the date of seeking healthcare RR = 1.06, 95% CI 1.02-1.10, P = 0.004). CONCLUSION: These findings provide insights into risk stratification and suggest specific directions for future research. This information informs the development of targeted intervention strategies to mitigate the impact of RSV infections in this vulnerable population.

Evaluating the performance of WHO and CDC case definitions for influenza-like illness in diagnosing influenza during the 2022-2023 flu season in Mexico.

OBJECTIVE: This study aimed to evaluate the performance of the World Health Organization (WHO) and Centers for Disease Control and Prevention (CDC) case definitions for influenza-like illness (ILI) in diagnosing influenza during the 2022-2023 flu season in Mexico. STUDY DESIGN: We conducted a cross-sectional analysis of national epidemiological surveillance data in Mexico, focusing on respiratory viral pathogens. METHODS: We analyzed data from 6027 non-hospitalized patients between 5 and 65 years old who underwent molecular testing for respiratory viral pathogens. The performance of both case definitions was evaluated in terms of sensitivity, specificity, and the area under the receiver operating characteristic (AUROC) curve. RESULTS: Overall, the diagnostic accuracy of the evaluated ILI definitions in identifying influenza patients was low, particularly among older patients. When compared to the CDC, the WHO definition had a lower sensitivity but a higher specificity, resulting in a higher AUROC (P = 0.031) for the WHO criteria. CONCLUSIONS: Our findings suggest that the WHO and CDC ILI case definitions have limited accuracy for diagnosing influenza in non-hospitalized patients and highlight the need for more specific diagnostic tools to improve the detection of influenza cases during the flu season.

Comparing the survival of adult inpatients with COVID-19 during the wild-type, Delta, and Omicron emergence.

OBJECTIVE: This study aimed to compare the survival experience of adult inpatients with laboratory-confirmed COVID-19 during the first three waves (wild type, Delta, and Omicron) of the pandemic in Mexico. STUDY DESIGN: A retrospective and nationwide study was conducted. METHODS: Data from 229,311 participants were analyzed using the Kaplan-Meier method, and estimates per each pandemic wave were obtained. A multivariate Cox proportional hazard regression model was fitted, and hazard ratios (HRs) and 95% confidence intervals (CIs) were computed. RESULTS: The overall mortality rate was 49.1 per 1000 person-days. Heterogeneous survival rates were observed during the analyzed emergences (log-rank test, P < 0.001), and the lowest survival functions were computed during the Omicron variant dominance. In multiple analyses and after adjusting by host characteristics and COVID-19 vaccination status, cases occurring during the Delta (vs wild type: HR = 1.03, 95% CI 1.01-1.05) and Omicron emergence were at increased risk for a fatal in-hospital outcome (HR = 1.17, 95% CI 1.13-1.22). CONCLUSIONS: Our results suggest variant-related differences in the survival rates of hospitalized patients with laboratory-positive COVID-19. When compared with the wild-type virus, lower rates were observed during the Delta and Omicron emergence.

First-generation BNT162b2 and AZD1222 vaccines protect from COVID-19 pneumonia during the Omicron variant emergence.

OBJECTIVE: This study aimed to identify factors predicting pneumonia in adults with coronavirus disease 2019 (COVID-19) during the Omicron variant (B.1.1.529) emergence. We also evaluated, in fully vaccinated (BNT162b2 or AZD1222) individuals, if the time (<6 or ≥6 months) elapsed since the last shot was received was associated with the risk of severe illness. STUDY DESIGN: A retrospective cohort study was conducted in Mexico. METHODS: Data from 409,493 were analyzed, and risk ratios (RRs) and 95% confidence intervals (CIs) were computed through generalized linear models. RESULTS: We documented a total of 3513 COVID-19 pneumonia cases (69.5 per 100,000 person-days). In multiple analyses, a protective effect was observed in vaccinated adults (RR = 0.996, 95% CI 0.995-0.997). Male gender, increasing age, and smoking were associated with a greater risk of pneumonia. Individuals with chronic comorbidities (pulmonary obstructive disease, type 2 diabetes mellitus, arterial hypertension, kidney disease, and immunosuppression) were also at higher risk. Among fully vaccinated subjects (n = 166,869), those who had received the last shot at 6 more months were at increased risk for developing pneumonia (RR = 1.002, 95% CI 1.001-1.003). CONCLUSIONS: Our results suggest that the first-generation BNT162b2 and AZD1222 vaccines reduce the risk of COVID-19 pneumonia during the Omicron emergence. We also found that adults with longer interval from the administration of the second shot to illness onset were at increased risk of severe manifestations.

Performance of the case definition of suspected influenza before and during the COVID-19 pandemic.

OBJECTIVE: This study aimed to evaluate the performance, before and during the COVID-19 pandemic, of the case definition of suspected influenza used in community surveillance in Mexico. METHODS: A cross-sectional analysis of a cohort study was performed and cases that met the suspected case criteria (n = 20,511) and that had laboratory-conclusive evidence (quantitative real-time polymerase chain reaction) to confirm or discard influenza virus infection were analysed. RESULTS: A high sensitivity and modest specificity were documented, which later decreased during the COVID-19 outbreak, as well as its diagnostic accuracy. However, no significant differences were observed in the area under the receiver operating characteristics curve among the analysed periods. CONCLUSIONS: The evaluated case definition remains to be a cost-effective alternative for identifying patients who may benefit from influenza-specific antiviral drugs, even during the global COVID-19 outbreak.

Survival in adult pneumonia inpatients fulfilling suspected COVID-19 criteria and baseline negative RT-qPCR.

OBJECTIVES: The objective of this study was to evaluate the survival experience of suspicion COVID-19 hospitalized patients with pneumonia and negative baseline reverse-transcription quantitative polymerase chain reaction (RT-qPCR) test results. STUDY DESIGN: We conducted a nationwide retrospective cohort study in Mexico. METHODS: Adult pneumonia inpatients fulfilling suspected COVID-19 criteria, and hospital entry from March to August 2020, were enrolled. The Kaplan-Meier method was to use to compare survival estimates among patients with negative RT-qPCR nasopharyngeal or oropharyngeal swabs and those with a baseline positive test. RESULTS: Data from 64,624 individuals fulfilling suspected COVID-19 criteria were analyzed and 1.6% of them had negative RT-qPCR tests. The overall mortality rate was higher among laboratory-positive patients (48.5% vs. 34.2%, P < 0.001) and, at any given threshold, the survival estimates were higher among RT-qPCR-negative pneumonia inpatients. CONCLUSIONS: The pathogenic mechanism of COVID-19 remains poorly understood and suspected cases with pneumonia and negative laboratory results represent a major challenge for healthcare systems. Our findings suggest that RT-qPCR-negative inpatients may have an improved disease prognosis, but the in-hospital mortality was still high among them. However, further research is needed to clarify the clinical and epidemiological implications of our results.

National retrospective cohort study to identify risk factors for in-hospital 30-day lethality in laboratory-confirmed cases of influenza.

OBJECTIVE: To identify factors associated with the risk of death in adolescent and adult inpatients with laboratory-positive (reverse-transcription polymerase chain reaction) influenza in Mexico during consecutive influenza seasons (2018-2020). METHODS: A retrospective cohort study used national surveillance system data, enrolling 3.422 individuals. The association between various risk factors and 30-day in-hospital lethality were evaluated through risk ratios (RRs) and 95% confidence intervals (CIs). RESULTS: The lethality rate was 18.1%. Flu vaccination history (RR=0.56, 95% CI 0.42-0.78), early antiviral drug administration (≤2 days from symptom onset [reference ≥5 days], RR=0.68, 95% CI 0.58-0.81), and a history of asthma (RR=0.66, 95% CI 0.47-0.95) showed protective effects against influenza-attributable death. Mechanical ventilator support produced the highest increase in death risk (RR=3.31, 95% CI 2.89-3.79). Male sex, older age, AH1N1 subtype, and other chronic diseases were also associated with fatal in-hospital influenza-related outcomes. CONCLUSIONS: Our findings highlight the major relevance of promoting immunization in high-risk individuals, together with ensuring early and effective antiviral management in suspected influenza cases.

Predictors of severe symptomatic laboratory-confirmed SARS-CoV-2 reinfection.

OBJECTIVE: The aim of the study was to evaluate factors predicting severe symptomatic laboratory-confirmed (via Reverse transcription polymerase chain reaction, RT-PCR polymerase chain reaction) severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) reinfection. STUDY DESIGN: This is a nationwide retrospective cohort study that was conducted in Mexico. METHODS: Data from 258 reinfection cases (at least 28 days between both episodes onset) were analyzed. We used risk ratios (RRs) and 95% confidence intervals (CIs) to evaluate predictors of severe (dyspnea requiring hospital admission) secondary SARS-CoV-2 infection. RESULTS: The risk of severe disease was 14.7%, and the observed overall fatality rate was 4.3%. Patients with more serious primary disease were more likely to develop severe symptoms (39.5% vs. 5.5%, P < 0.001) during reinfection. In multiple analysis, factors associated with an increased risk of severe symptomatic SARS-CoV-2 reinfection were increasing age (RRper year = 1.007, 95% CI = 1.003-1.010), comorbidities (namely, obesity [RR = 1.12, 95% CI = 1.01-1.24], asthma [RR = 1.26, 95% CI = 1.06-1.50], type 2 diabetes mellitus [RR = 1.22, 95% CI = 1.07-1.38]), and previous severe laboratory-confirmed coronavirus disease 2019 (RR = 1.20, 95% CI = 1.03-1.39). CONCLUSIONS: To the best of our knowledge, this is the first study evaluating disease outcomes in a large set of laboratory-positive cases of symptomatic SARS-CoV-2 reinfection, and factors associated with illness severity were characterized. Our results may contribute to the current knowledge of SARS-CoV-2 pathogenicity and to identify populations at increased risk of a poorer outcome after reinfection.

Survival in adult inpatients with COVID-19.

BACKGROUND: The mortality of the coronavirus disease 2019 (COVID-19) pandemic is high, and data regarding its prognosis are scarce. We aimed to assess the survival experience and determining factors in adult inpatients with laboratory-confirmed COVID-19. METHODS: We conducted a nationwide and retrospective cohort study. Data from 66,123 individuals were analyzed using the Kaplan-Meier method, and a multivariate Cox proportional hazard regression model was fitted. RESULTS: The 7-day survival was 72.2% and went to 47.6%, 35.0%, and 23.9% on days 15, 21, and 30 of hospital stay, respectively. In the multiple analysis, factors associated with an increased risk of dying were male gender, age, pneumonia at hospital admission, immunosuppression, and personal history of chronic non-communicable diseases. Reduced risk of a fatal outcome was observed among patients with asthma history. CONCLUSIONS: To the best of our knowledge, this is the largest study analyzing the survival probability in a large subset of Latin-American adults with COVID-19, in whom the disease burden has been high. Our results contribute to achieving a better understanding of disease evolution.

Predictors of laboratory-positive COVID-19 in children and teenagers.

OBJECTIVE: The aim of the study was to identify factors predicting laboratory-positive coronavirus disease 2019 (COVID-19) in pediatric patients with acute respiratory symptoms. STUDY DESIGN: We conducted a cross-sectional analysis of a prospective cohort study. METHODS: Data from 1849 individuals were analyzed. COVID-19 was confirmed (reverse transcription-quantitative polymerase chain reaction) in 15.9% of patients, and factors predicting a positive test result were evaluated through prevalence odds ratios and 95% confidence intervals. RESULTS: Increasing age, personal history of obesity, and household contact with a case were found to be associated, in the multiple regression model, with increased odds of a positive test result. Young patients residing in areas with higher population sizes, as well as those with severe respiratory symptoms, were less likely to be laboratory confirmed. CONCLUSIONS: Early identification and isolation of children and teenagers with suggestive symptoms of COVID-19 is important to limit viral spread. We identified several factors predicting the laboratory test result. Our findings are relevant from a public health policy perspective, particularly after the restart of in-person academic activities.