{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,11,2]],"date-time":"2026-11-02T08:56:24Z","timestamp":1793609784543,"version":"4.5.0"},"reference-count":44,"publisher":"American Society of Tropical Medicine and Hygiene","issue":"1","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2025,7,2]]},"abstract":"<jats:title>ABSTRACT.<\/jats:title>\n<jats:p>Malaria epidemiology in Kenya is heterogeneous because of geographic and climatic differences. Semi-arid and arid zones are prone to seasonal increases in malaria cases above expected levels after rainy seasons, leading to malaria outbreaks. In November 2023, Marsabit County experienced a 155% increase in rainfall above its monthly average. The malaria surveillance system detected a 345% increase in cases, rising from 210 during Epiweek 1 to Epiweek 6 of the previous year to 934 in 2024. An outbreak investigation was conducted to guide prevention and control efforts. We reviewed routine surveillance data from December 2023 to February 2024, abstracted data from 12 facilities that surpassed action thresholds (5-year weekly median + third quantile), conducted data quality assessments, and conducted two community-focused group discussions. The data were analyzed as frequencies and proportions. Of the 757 malaria cases abstracted, the median age was 17 years (interquartile range: 10\u201328 years), with 227 cases (30.0%) in individuals aged 10\u201320 years. Males accounted for 424 cases (56.0%), 421 cases (55.6%) were tested using <jats:italic>Plasmodium falciparum<\/jats:italic> (<jats:italic>P. falciparum<\/jats:italic>)-specific rapid diagnostic tests, and 44.4% were tested using microscopy. Among the cases identified via microscopy tests, 94.9% involved <jats:italic>P. falciparum<\/jats:italic>, 2.7% involved<jats:italic> Plasmodium vivax<\/jats:italic>, and 2.4% involved <jats:italic>Plasmodium ovale<\/jats:italic>. There were 90 cases (11.9%) of severe malaria and three deaths. The reporting accuracy was 90% for a third of the facilities, and the completeness of monthly summaries was 39%. Potential exposures reported by the community included proximity to a national park, proximity to stagnant water, and sleeping outside during herding. The outbreak was predominantly due to <jats:italic>P. falciparum<\/jats:italic> malaria but also involved non-falciparum malaria, with most cases occurring in males aged 10\u201320 years. We recommend the continuous monitoring of malaria species to improve malaria surveillance.<\/jats:p>","DOI":"10.4269\/ajtmh.24-0681","type":"journal-article","created":{"date-parts":[[2025,5,6]],"date-time":"2025-05-06T20:33:37Z","timestamp":1746563617000},"page":"49-56","source":"Crossref","is-referenced-by-count":2,"title":["Characterization of Malaria Outbreak in Marsabit County, Kenya, March 2024"],"prefix":"10.4269","volume":"113","author":[{"given":"Peter Wachira","family":"Muguku","sequence":"first","affiliation":[{"name":"Kenya Field Epidemiology and Training Program (K-FELTP), Nairobi, Kenya;"},{"name":"Division of National Malaria Control Program (NMCP), Nairobi, Kenya"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Fredrick","family":"Odhiambo","sequence":"additional","affiliation":[{"name":"Kenya Field Epidemiology and Training Program (K-FELTP), Nairobi, Kenya;"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"James","family":"Sang","sequence":"additional","affiliation":[{"name":"Division of National Malaria Control Program (NMCP), Nairobi, Kenya"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Emmanuel","family":"Sigei","sequence":"additional","affiliation":[{"name":"Kenya Field Epidemiology and Training Program (K-FELTP), Nairobi, Kenya;"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Lydia","family":"Khalayi","sequence":"additional","affiliation":[{"name":"Kenya Field Epidemiology and Training Program (K-FELTP), Nairobi, Kenya;"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ahmed M.","family":"Abade","sequence":"additional","affiliation":[{"name":"Kenya Field Epidemiology and Training Program (K-FELTP), Nairobi, Kenya;"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"2795","reference":[{"key":"b1","doi-asserted-by":"crossref","DOI":"10.21203\/rs.3.rs-3179248\/v1","article-title":"Increased Case-Load of Malaria in an Epidemic Prone Zone that had been Masked by Insufficient Surveillance Data Reveled During Yellow Fever Outbreak Investigation in Kenya, 2022","author":"Nchoko","year":"2023"},{"key":"b2","series-title":"Ann Med Surg (Lond)","first-page":"104366","article-title":"Increasing challenges of malaria control in sub-Saharan Africa: Priorities for public health research and policymakers","volume":"81","author":"Oladipo","year":"2022"},{"key":"b3","article-title":"World Malaria Report 2023","year":"2023"},{"key":"b4","series-title":"Emerg Infect Dis","first-page":"681","article-title":"Response to malaria epidemics in Africa","volume":"13","author":"Abeku","year":"2007"},{"key":"b5","series-title":"J Infect Dis","first-page":"887","article-title":"Declining malaria transmission differentially impacts the maintenance of humoral immunity to Plasmodium falciparum in children","volume":"216","author":"Mugyenyi","year":"2017"},{"key":"b6","series-title":"Sci Rep","first-page":"9938","article-title":"Malaria surveillance, outbreak investigation, response and its determinant factors in Waghemra Zone, Northeast Ethiopia: Unmatched case\u2013control study","volume":"13","author":"Debash","year":"2023"},{"key":"b7","article-title":"Guidelines for Malaria Epidemic Preparedness and Response in Kenya: 2nd Edition \u2013 Malaria","year":"2020"},{"key":"b8","article-title":"Improving Kenya\u2019s Malaria Response by Revising Epidemic Thresholds","author":"Gatakaa","year":"2024"},{"key":"b9","article-title":"FELTP \u2013 RVF Outbreak in Marsabit & Wajir Counties","author":"Owiny","year":"2024"},{"key":"b10","series-title":"BMC Public Health","first-page":"484","article-title":"Risk factors associated with malaria outbreak in Laelay Adyabo district northern Ethiopia, 2017: Case-control study design","volume":"19","author":"Tesfahunegn","year":"2019"},{"key":"b11","series-title":"J Infect Dis","first-page":"S155","article-title":"Entomological and anthropological factors contributing to persistent malaria transmission in Kenya, Ethiopia, and Cameroon","volume":"223","author":"Bamou","year":"2021"},{"key":"b12","series-title":"Nat Commun","first-page":"4626","article-title":"Plasmodium falciparum infection in humans and mosquitoes influence natural Anopheline biting behavior and transmission","volume":"15","author":"Markwalter","year":"2024"},{"key":"b13","series-title":"Int J Infect Dis","first-page":"268","article-title":"Malaria outbreak response in a nomadic pastoralist setting, Kenya 2019","volume":"101","author":"Rono","year":"2020"},{"key":"b14","series-title":"Trop Med Infect Dis","first-page":"161","article-title":"Are malaria risk factors based on gender? 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