With a billion cases worldwide and a million deaths annually, vector borne diseases remain important globally. Malaria is prevalent worldwide with an especially heavy burden in Africa. Outstanding gaps remain in our understanding of vector biology and the maintenance and spread of MBPs from their sylvatic cycles, limiting our success in vector-borne disease control. 1. We have evaluated the contribution of aestivation to the persistence of mosquitoes in the Sahel by tracking wild mosquitoes marked by deuterium (2H) from the end of the wet season until the beginning of the subsequent wet season. If local aestivation is the way An. coluzzii persists, the frequency of marked mosquitoes should remain stable, whereas finding no marked mosquitoes would be evidence against aestivation. After an initial enrichment, 33% of An. coluzzii were marked. Seven months later, multiple analyses revealed the presence of marked mosquitoes. The results suggest that aestivation is a major persistence mechanism of A. coluzzii, contributing at least 20% of the adults at the onset of rains (Faiman et al. 2022:Nature Ecol. Evol.). This persistence strategy could influence malaria control and elimination campaigns. 2. Our recently studies on aerial sampling of mosquitoes 40-290 m above the Sahel of Mali (Huestis et al. 2019: Nature, Yaro et al. 2022: Frontiers in Epidemiology) revealed members of 7 genera- Culex, Aedes, Anopheles, Mansonia, Mimomiya, Lutzia, and Eretmapodites at altitude. A total of 50 species were identified (N=2,340 specimens). At altitude, females outnumbered males 6:1, and >90% of the females had taken at least one blood meal on a vertebrate host prior to departure suggesting that some windborne mosquitoes carry MBPs. Our current results obtained by Dr. Bamou (postdoc) show high infection rates in these high-altitude migrants with arboviruses, plasmodia, and filariae. Infection and infectiousness rates of high-altitude mosquitoes were 7.2% and 4.4% with plasmodia, 1.6% and 0.6% with filariae, 3.5% and 1.1% with flaviviruses and 6.6% and 4.8% with alphaviruses, respectively. Highly diverse pathogens were identified: 53 Plasmodial lineages of 13 putative species (e.g., P. matutinum), 3 filariae (e.g., Pelecitus spp.), 8 flaviviruses (e.g., dengue, Barkedji, West Nile), and one orthobunyavirus (M’Poko virus), among non-mosquito-borne pathogens (e.g., Haemoproteus coraciae). The high infection and infectiousness rates across mosquito species including with dengue and the zoonotic West Nile and M’Poko viruses attest for the importance of windborne pathogen spread for public health. These results suggest that MBPs are likely to be carried by infected mosquitoes over large distances from sylvatic foci and initiate epizootics tens or hundreds of kilometers away. Additionally, aerial pathogen/disease surveillance could be used to map the sources and destinations of vectors and pathogens and thus mitigate public health threats. 3. To determine if mosquitoes engage in high-altitude flights beyond the Sahel, we have expanded aerial sampling into the savannas ecozones (Mali) and into the woodland and equatorial forests (Ghana) as well as in Kenya (East Africa). A total of 56 mosquito species were found in these West African ecozones (N=760), belonging to 8 genera. Windborne mosquitoes occurred more commonly above perennial ecosystems including the equatorial forests than above the Sahel. Based on species composition, movement between the equatorial forest to the Sahel >750 km may occur. A one-year study in Kenya has demonstrated that windborne mosquitoes and other insects are common across the continent (Atieli et al. 2023). 4) Mrs. Rita Nartey-Frimpong, a PhD student (joint NIH (GPP)- Kwame Nkrumah University of Science and Technology, Ghana) has been working on the insects collected at altitude in Mali and Ghana, focusing on species impacting food security. Her first paper of this project is now 'In Press' (Nartey et al. 2024: Neobiota). Invasive insects threaten ecosystem stability, public health, and food security. We report on the invasion of the South American leafhopper, Curtara insularis into Africa, where it has established populations in Ghana. Importantly, 80% of the specimens collected were intercepted between 160 and 190 m above ground. The fraction of this species among all insects collected was also higher at altitude, demonstrating its propensity to engage in high-altitude windborne dispersal. Its aerial densities at altitude translate into millions of migrants/km over a year, representing massive propagule pressure. Given the predominant south-westerly winds, these sightings suggest an introduction of C. insularis into at least one of the Gulf of Guinea ports. To assess the contribution of windborne dispersal to its spread in a new territory, we examine records of C. insularis range-expansion in the USA. Reported first in 2004 from central Florida, it reached north Florida (Panhandle) by 2008-2011 and subsequently spread across the southeastern and south-central US. Its expansion fits a “diffusion-like” process with 200—300 km long “annual displacement steps”—a pattern consistent with autonomous dispersal rather than vehicular transport. Most “steps” are consistent with common wind trajectories from the nearest documented population, assuming 2—8 hours of wind-assisted flight at altitude. Curtara insularis has been intercepted at US ports and on trucks. Thus, it uses multiple dispersal modes, yet its rapid overland spread is best explained by its massive propagule pressure linked with its high-altitude windborne dispersal. We propose that high-altitude windborne dispersal is common yet under-appreciated in invasive insects. 5) To understand the scope of mosquito windborne migration and the pathogens that they transmit to vertebrates in Africa, a literature survey has been undertaken to generate a unique database of the African mosquito borne diseases from a One Health perspective. Analysis of the database produced valuable fresh insights into the biogeography of MBDs on the continent with implications for disease surveillance and for emerging/re-emerging MBPs. Lehmann et al. 2023: Proc. Roy. Soc. B. 6) In collaboration with West African Center for Emerging Infectious Diseases (WAC-EID of NIAID CRIED, led by Dr. Scott Weaver, UTMB and Mawlouth Diallo, Institute Pasteur, Dakar) we initiated studies in Kedougou Senegal and Bantakoto Mali on windborne spread of arboviruses in mosquitoes. We will compare aerial and ground samples of mosquitoes and MBPs over Kedougou, Senegal—a well-known hotspot for arbovirus activity that has been extensively studied for >50 years with the Bantakoto (Mali) aerial station, located 110 km from Kedougou to address if arboviruses spread in windborne mosquitoes from enzootoic (sylvatic) cycles into new areas, generating outbreaks tens or hundreds of kilometers away.