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.

Respiratory syncytial virus infection: survival experience in a cohort of children inpatients.

OBJECTIVE: The objective of this study was to assess the survival experience of children hospitalized with laboratory-confirmed respiratory syncytial virus (RSV) infection due to bronchiolitis. STUDY DESIGN: This was a nationwide retrospective cohort study conducted in Mexico. METHODS: We analyzed data from 436 children aged 5 years and younger, with symptom onset between August 2021 and November 2022. The Kaplan-Meier method was used to compute survivor functions and their 95% confidence intervals (CI). RESULTS: High survival rates were observed, particularly within the first three weeks of hospital admission. The 3-day survival rate was 99.8% (CI 98.4-99.9%), which decreased to 98.9% (CI 96.5-99.7%), 97.5% (CI 91.9-99.3%), 86.7% (CI 48.2-97.2%), and 69.4% (CI 24.2-91.0%) on days 7, 14, 21, and 28 of hospital stay, respectively. We documented a total of 5 fatal outcomes, resulting in a mortality rate of 2.1 (95% CI 0.9-5.1) per 1,000 person-days. CONCLUSIONS: Our study analyzed a large cohort of pediatric patients with bronchiolitis caused by RSV infection, providing valuable insights into the in-hospital progression of this disease.

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.