P-668. Detection and Clinical Impact of Influenza in a Cohort of Agricultural Workers in Guatemala, 2020-2024

TL;DR

This study tracked influenza in agricultural workers in Guatemala from 2020 to 2024, finding that 7.2% of reported illnesses were due to influenza, with fever as a key symptom.

Contribution

The study demonstrates the feasibility of active surveillance and rapid diagnostics for influenza in field-based agricultural worker populations.

Findings

7.2% of influenza-like illness episodes were confirmed as influenza, with 18 cases of influenza A and 11 of influenza B.

Flu-positive cases reported fever more frequently than flu-negative cases (96.6% vs. 65.9%).

The incidence of influenza was 0.11 per 1000 person-weeks with minimal yearly variation.

Abstract

Influenza viruses circulate year-round in Central America, but their impact on agricultural workers, essential to food security in the Americas, is poorly understood.

We evaluated the incidence of influenza among a cohort of agricultural workers in southwest Guatemala participating in active surveillance for influenza-like illness (ILI) from June 2020 to October 2024. Workers reporting cough, fever, or shortness of breath in the previous 7 days provided nasopharyngeal swabs for influenza RT-PCR testing using the Roche cobas liat instrument. Symptom data were collected on the day of reporting, day 7, and day 28, with differences in reported symptoms by influenza virus infection status assessed using Fisher’s Exact tests.

Of 2,809 agricultural workers who participated in ≥1 year of surveillance, 76% were male with a mean age of 30 years. Overall, 400 (14%) ever reported an ILI episode; 7.3% (29/400) were influenza positive (flu+): 18 influenza A, 11 influenza B. The incidence of ILI and flu+ cases per 1000 person-weeks from 2021 to 2024 was 1.4 (95% Confidence Interval [CI] 1.3-1.6) and 0.11 (95% CI 0.07-0.16), respectively, with minimal yearly variation (Figure). Of the 400 ILI cases, 68% reported fever, 78% cough, and 28% shortness of breath. Flu+ cases reported fever more frequently than flu- cases (96.6% vs. 65.9%, p=0.001). Among ILI cases, 8.4% reported difficulty getting out of bed on day 7 and 3.4% on day 28, with no significant difference by influenza status.

Among young adult, mostly male agricultural workers, 7.2% of reported ILI episodes were attributed to influenza, with fever being a key symptom. This study demonstrates the feasibility of monitoring circulating respiratory virus illnesses in field-based environments using active surveillance and rapid diagnostics.

Edwin J. Asturias, MD, Pfizer: Grant/Research Support Molly Lamb, PhD, Merck: Grant/Research Support Daniel Olson, MD, Fundacion para la Salud Integral de los Guatemaltecos: Board Member|Merck: Grant/Research Support|Roche Diagnostics: Grant/Research Support

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