47 - Uncovering DENV dynamics through mosquito surveillance and testing.

Abstract: Understanding dengue transmission in communities is important for the planning and implementation of vector control activities. Not all dengue infected persons have symptoms, many mildly asymptomatic patients do not seek care, and not all providers suspect dengue or order dengue tests; therefore, case reports represent a subset of community transmission. Testing mosquitoes can help us detect dengue transmission otherwise undetected by traditional surveillance methods. To investigate the duration of dengue circulation following case reporting and identify any undetected circulation using traditional case surveillance methods, we placed 30 CDC Autocidal Gravid Ovitraps (AGO) within a 200-meter radius of households where index cases were reported. This was done in 13 neighborhoods with recent confirmed dengue cases, aiming to capture potentially infected female Aedes aegypti mosquitoes. We inspected the AGO traps for mosquitoes every 7 days over a period of at least 21 days. Female Ae. aegypti mosquitoes were identified in the field and grouped in pools (1-20 specimens/pool), stored at -80 C, and processed as super pools in the laboratory using RT-PCR. Out of the 13 dengue cases monitored between January and September 2024, 9 (69.2%) of them had at least one positive mosquito pool detection, 5 (38.4%) had the first positive pool detected during the first surveillance week, while 4 (30.8%) were detected during the second week. The longest period between trap placement and the last positive pool detection within an area was 56 days. In 3 (23%) of the cases under surveillance, we detected a serotype different from the one initially reported for the human case. Our findings indicate that various serotypes may circulate in localized areas, which may not be captured by human case surveillance alone. Based on these findings, we recommend implementing Ae. aegypti control measures for a minimum of 2 months following the detection of a case.