National respiratory syncytial virus acute respiratory infection burden of disease estimate in Mexican children under 2 years.

BACKGROUND: National population-based respiratory syncytial virus (RSV) direct burden-of-disease estimates on outpatient, emergency room (ER) and hospitalization settings are scarce among Mexican children. These estimates are key to inform the development of preventive public policies and to strengthen seasonal clinical planning in Mexico. METHODS: A systematic review of literature allowed estimating robust RSV-proportions in acute respiratory infection (ARI) and lower respiratory tract infection (LRTI) studies in Mexican children 0 to 23 months-old (<2yo) and length-of-stay, mortality rates, mechanical ventilation use, and seasonality patterns for RSV-attributed cases that could be scaled nationally. These results allowed the estimation of outpatient and ER visits, hospitalizations, total length-of-stay and deaths of RSV-related illnesses from national databases available in the public domain for the 2011-2023 period. Incidence rates were also calculated considering the official population projections for the period analyzed. RESULTS: RSV-proportions accounted for 31.76% and 16.03% of outpatient visits in children 0 to 11 months-old (<1yo) and children 12 to 23 months-old (1yo) respectively; In <2yo RSV-proportions were 17.96% in ER and 20.25% (pneumonia) to 34.72% (bronchiolitis) in hospitalization. Mean length-of-stay and mortality were highest in preterm <1yo (7.04 days, 2.11%) followed by at-term <1yo (5.77 days; 1.4%) and 1yo (4.77; 0.87%). Mechanical ventilation followed a similar trend (12.24%, 5.77% and 2.03%). Seasonally (96% autumn-winter), RSV caused in <2yo ∼772,450 outpatient visits, ∼185,326 ER visits, and ∼26,873 hospitalizations. Annual rates per 1,000 children were ∼248 and ∼107 in <1yo and 1yo respectively in outpatient settings; ∼55, ∼30 in ER settings and ∼32 in preterm <1yo, ∼9 at-term <1yo and ∼4 in 1yo in hospitalization settings. CONCLUSIONS: RSV burden-of-disease was seasonal, imposing a major burden on healthcare facilities during autumn-winter. Children <1yo were the most affected in the three clinical settings analyzed. These results can be used to calculate the financial RSV burden-of-disease as well as to inform the development of preventive policies and to strengthen seasonal clinical planning in Mexico.