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Background In areas highly endemic for malaria, Plasmodium falciparum infection prevalence peaks in school-age children, adversely affecting health and education. School-based intermittent preventive treatment reduces this burden but concerns about cost and widespread use of antimalarial drugs limit enthusiasm for this approach. School-based screening and treatment is an attractive alternative. In a prospective cohort study, we evaluated the impact of school-based screening and treatment on the prevalence of P. falciparum infection and anemia in 2 transmission settings. Methods We screened 704 students in 4 Malawian primary schools for P. falciparum infection using rapid diagnostic tests (RDTs), and treated students who tested positive with artemether-lumefantrine. We determined P. falciparum infection by microscopy and quantitative polymerase chain reaction (qPCR), and hemoglobin concentrations over 6 weeks in all students. Results Prevalence of infection by RDT screening was 37% (9%–64% among schools). An additional 9% of students had infections detected by qPCR. Following the intervention, significant reductions in infections were detected by microscopy (adjusted relative reduction [aRR], 48.8%; P Conclusions School-based screening and treatment reduced P. falciparum infection and anemia. This approach could be enhanced by repeating screening, using more-sensitive screening tests, and providing longer-acting drugs. Clinical Trials Registration NCT04858087.

Anemia is a leading cause of morbidity in sub-Saharan Africa. The etiologies of anemia are multifactorial, and it is unclear what proportion of anemia is attributable to malaria in children of different ages in Malawi. We evaluated the population attributable fraction (PAF) of anemia due to malaria using multiple cross-sectional surveys in southern Malawi. We found a high prevalence of anemia, with the greatest proportion attributable to malaria among school-age children (5–15 years) in the rainy season (PAF = 18.8% [95% CI: 16.3, 21.0], compared with PAF = 5.2% [95% CI: 4.0, 6.2] among young children pooled across season [< 5 years] and PAF = 9.7% [95% CI: 6.5, 12.4] among school-age children in the dry season). Malaria control interventions will likely lead to decreases in anemia, especially among school-age children.

Timely treatment-seeking behavior can reduce morbidity and mortality due to infectious diseases. Patterns of treatment-seeking behavior can differ by access to health care, and perceptions of disease severity and symptoms. We evaluated the association between self-reported symptoms at last illness and the level of treatment-seeking behaviors. We analyzed cross-sectional data from 1,037 participants from the lowlands and highlands of Western Kenya from 2015 using logistic regression models. There was considerable heterogeneity in the symptoms and treatment-seeking behaviors reported among individuals who were febrile at their last illness. A greater number of self-reported categories of symptoms tended to be associated with a higher likelihood of treatment-seeking in both sites. Participants were significantly more likely to seek treatment if they reported fever, aches, and digestive symptoms at last illness than just fever and aches or fever alone, but the frequency of treatment-seeking for fever in combination with aches and respiratory symptoms did not follow a consistent pattern. Among those who sought treatment, most used a formal source, but the patterns were inconsistent across sites and by the number of symptoms categories. Understanding the drivers of treatment-seeking behavior after febrile illness is important to control and treat infectious diseases in Kenya.

Universal “coverage” with long-lasting insecticidal nets (LLINs) is recommended for malaria control in endemic areas, but ownership does not ensure usage. We evaluated relationships between household-level ownership and individual-level usage in western Kenya in 2015. Low-prevalence highland (> 1,500 m) and highly endemic lowland (< 1,200 m) sites were surveyed from July to August 2015. Household members reported long-lasting insecticidal net ownership, use, and barriers to use. Net ownership was categorized as sufficient (≤ 2 people/net), insufficient (> 2 people/net), or none. Each LLIN was assumed to provide access to two people. We surveyed 574 lowland and 643 highland households, with 1,677 and 2,742 members, respectively. More than 98% of lowland households owned LLIN(s); 72.1% owned a sufficient number. Only 37.5% of highland households had sufficient nets. More people used LLINs than were estimated to have access in the lowlands (94.2% versus 85.3%), but proportions were similar in the highlands (54.3% versus 53.3%). Insufficient ownership was most common for larger households in both areas and strongly predicted LLIN usage. In households with insufficient nets, men, school-age children (aged 5–15 years), and nonnuclear family members were less likely to use LLINs; only relationship to the head of the household significantly predicted use in households with sufficient nets. Long-lasting insecticidal nets were widespread in western Kenya in 2015, but insufficient household ownership remained common in the epidemic highlands and in large households. Access seemed to be the primary driver of individual use. To interrupt transmission, LLIN campaigns should improve distribution to large households and promote use among men, school-age children, and nonnuclear family members.

Background: Climate change is expected to increase the frequency of flooding events. Although rainfall is highly correlated with mosquito-borne diseases (MBD) in humans, less research focuses on understanding the impact of flooding events on disease incidence. This lack of research presents a significant gap in climate change–driven disease forecasting. Objectives: We conducted a scoping review to assess the strength of evidence regarding the potential relationship between flooding and MBD and to determine knowledge gaps. Methods: PubMed, Embase, and Web of Science were searched through 31 December 2020 and supplemented with review of citations in relevant publications. Studies on rainfall were included only if the operationalization allowed for distinction of unusually heavy rainfall events. Data were abstracted by disease (dengue, malaria, or other) and stratified by post-event timing of disease assessment. Studies that conducted statistical testing were summarized in detail. Results: From 3,008 initial results, we included 131 relevant studies (dengue n=45, malaria n=61, other MBD n=49). Dengue studies indicated short-term (

Background: Climate change is expected to increase the frequency of flooding events. Although rainfall is highly correlated with mosquito-borne diseases (MBD) in humans, less research focuses on un...

Background Insecticide-treated nets (ITNs) and long-lasting insecticidal nets (LLINs) are effective for malaria prevention and are designed to provide nearly 5 years of mosquito protection. However, many ITNs and LLINs become damaged and ineffective for mosquito bite prevention within 1 to 2 years in field conditions. Non-adherence to recommended bed net care and repair practices may partially explain this shortened net longevity. Methods Using data from a cross-sectional study, a net care adherence score was developed and adherence to net care practices described from two regions of western Kenya. Relationships between attitudes and environmental factors that influence net longevity were measured with adherence to bed net care practices. Results While overall care practices are highly adherent particularly in the highlands, practices related to daily storage, washing frequency, and drying location need improvement in the lowlands. Seventy-seven percent of nets in the lowlands were washed

BackgroundIn areas highly endemic for malaria,Plasmodium falciparum(Pf) infection prevalence peaks in school-age children, adversely affecting their health and education. School-based intermittent preventive treatment reduces this burden, however concerns about cost and widespread use of antimalarial drugs have limited enthusiasm for this approach. School-based screening-and-treatment is an attractive alternative. We conducted a school-based cohort study to evaluate the impact of screening-and-treatment on the prevalence ofPfinfection and anemia in two different transmission settings.MethodsWe screened 704 students in four Malawian primary schools forPfinfection using rapid diagnostic tests (RDTs). Those testing positive were treated with artemether-lumefantrine. Outcomes werePfinfections detected by microscopy or PCR and anemia after six weeks.ResultsPrevalence of infection by RDT at screening was 37% (range among schools 9-64%). We detected a significant reduction after six weeks in infections by microscopy (adjusted relative reduction (aRR) 47.1%, pConclusionsSchool-based screening-and-treatment reducedPfinfection but not anemia. This approach could be enhanced in low transmission settings by using more sensitive screening tests and in high transmission settings by repeating the intervention or using longer acting drugs.SummaryMalaria screening-and-treatment reducedP. falciparuminfections but not anemia. Because rapid diagnostic tests failed to detect low-density infections, screening tests with higher sensitivity may be needed in low transmission areas where low-density infections make-up a larger proportion of infections.

In areas where malaria remains entrenched, novel transmission-reducing interventions are essential for malaria elimination. We report the impact screening-and-treatment of asymptomatic Malawian schoolchildren (n = 364 in the rainy season and 341 in the dry season) had on gametocyte—the parasite stage responsible for human-to-mosquito transmission—carriage. We used concomitant household-based surveys to predict the potential reduction in transmission in the surrounding community. Among 253 students with P. falciparum infections at screening, 179 (71%) had infections containing gametocytes detected by Pfs25 qRT-PCR. 84% of gametocyte-containing infections were detected by malaria rapid diagnostic test. While the gametocyte prevalence remained constant in untreated children, treatment with artemether-lumefantrine reduced the gametocyte prevalence (p

In areas where malaria remains entrenched, novel transmission-reducing interventions are essential for malaria elimination. We report the impact of screening-and-treatment of asymptomatic schoolchildren (N=705) on gametocyte - the parasite stage responsible for human-to-mosquito transmission - carriage and use concomitant household-based surveys to predict the potential reduction in transmission in the surrounding community. Among 179 students with gametocyte-containing infections, 84% had positive malaria rapid diagnostic tests. While gametocyte burden remained constant in untreated children, treatment with artemether-lumefantrine reduced the gametocyte prevalence (p

Background Alternative long-lasting insecticidal net (LLIN) use for purposes other than sleeping protection from mosquitoes is widely debated as a limitation to successful malaria control efforts, yet rarely rigorously studied. Methods A cross-sectional survey of 1217 households in an epidemic highland site and an endemic lowland site in western Kenya collected information on alternative use in three ways: direct observations, participant self-report, and participant reporting of community-level practices. LLIN misuse was defined as use of an intact net for alternative purposes and repurposing as alternatively using an old or damaged net. Associations between households with observed repurposed nets and universal access and household net use were examined. Results Households describe repurposing nets when they are torn and/or old. Repurposed nets were observed in 8.1% (52/643) highlands households and 33.0% (184/574) lowlands households. Repurposed nets served as chicken coops (33% highlands, 20% lowlands), fences (37% highlands, 25% lowlands), tree covers (22% lowlands), curtains (3% highlands), covering bathrooms (1.5% highlands, 9% lowlands), and washing sponges (13% lowlands). No association was found between repurposing and universal access or household net use. Misuse was rare. Of 379 repurposed nets, 4 (1.06%) were in good condition with no holes. Of 1,758 active nets, 13 (0.74%) were misused. Conclusions Alternative net use in this study involved repurposing rather than misuse. Repurposing was not detrimental to malaria prevention efforts in these communities. Standardized measurement of alternative net use should be used to better understand the practice and its potential impact on the success of malaria interventions.

Background Submicroscopic Plasmodium falciparum infections are widespread in many areas. However, the contribution of these infections to symptomatic malaria is not well understood. This study evaluated whether participants with submicroscopic P. falciparum infections have higher prevalence of fever than uninfected participants in southern Malawi. Methods A total of 16,650 children and adults were enrolled in the course of six cross-sectional surveys during the dry season (October–November) and after the rainy season (April–May) between 2012 and 2014 in three districts in southern Malawi. Demographic and socioeconomic data were collected in conjunction with data on clinical histories, use of malaria preventive measures, and anti-malarial medication taken within 2 weeks of the survey. Axillary temperatures were measured, and blood samples were collected for P. falciparum detection by microscopy and PCR. Participants without malaria parasites detected on microscopy but with a positive PCR for P. falciparum were defined as having submicroscopic infection. Fever was defined as having any one of: reported fever in the past 2 weeks, reported fever in the past 48 h, or a temperature of ≥ 37.5 °C measured at the time of interview. Results Submicroscopic P. falciparum infections and fever were both detected in 9% of the study population. In the final analysis adjusted for clustering within household and enumeration area, having submicroscopic P. falciparum infection was associated with reduced odds of fever in the dry season (odds ratio = 0.52; 95% CI 0.33–0.82); the association in the rainy season did not achieve statistical significance (odds ratio = 1.20; 95% CI 0.91–1.59). The association between submicroscopic infection and fever was consistent across all age groups. When the definition of fever was limited to temperature of ≥ 37.5 °C measured at the time of interview, the association was not statistically significant in either the rainy or dry season. Conclusions In this series of cross-sectional studies in southern Malawi, submicroscopic P. falciparum infection was not associated with increased risk of fever. Submicroscopic detection of the malaria parasite is important in efforts to decrease transmission but is not essential for the clinical recognition of malaria disease.

La resistencia a los antibióticos (RA) sigue siendo uno de los más importantes problemas de salud global a la fecha. La RA en América latina específicamente, representa una de las grandes preocupaciones debido a los diferentes tipos de resistencia a los antibióticos que existen y el incremento de las tasas de aislamiento de los mismos. Iniciamos el análisis de las tasas de RA de aislamientos bacterianos de pacientes que asistieron a dos hospitales de la región rural de Ecuador desde el año 2017 hasta el año 2018. Un total de 907 aislados bacterianos fueron analizados, los cuales fueron recogidos desde el 1 de enero 2017 al 31 de diciembre 2018 y se evaluaron frente a 33 tipos de antibióticos diferentes. Cabe resaltar que más de la mitad de los aislamientos fueron resistentes a ampicilina (79.8%), ampicilina/sulbactam (57.5%), amoxicilina/ácido clavulánico (62.6%) en enterobacterias y a oxacilina (55.4%) en Staphylococcus aureus. De todos los aislamientos analizados 11 de los 33 antibióticos probados muestran un alto grado de resistencia (superior al 50 %). Se concluye que existen altas tasas de RA en zonas rurales del Ecuador, que siguen los patrones mundiales de resistencia ya publicados, y que deberían ser una contribución significativa a tomar en cuenta al momento de analizar la persistencia de la RA no solo en América latina sino en el mundo.

Background Malaria persists in some high-transmission areas despite extensive control efforts. Progress toward elimination may require effective targeting of specific human populations that act as key transmission reservoirs. Methods Parameterized using molecular-based Plasmodium falciparum infection data from cross-sectional community studies in southern Malawi, a simulation model was developed to predict the proportions of human-to-mosquito transmission arising from (a) children under 5 years old (U5s), (b) school-age children (SAC, 5–15 years), (c) young adults (16–30 years), and (d) adults > 30 years. The model incorporates mosquito biting heterogeneity and differential infectivity (i.e. probability that a blood-fed mosquito develops oocysts) by age and gametocyte density. Results The model predicted that SAC were responsible for more than 60% of new mosquito infections in both dry and rainy seasons, even though they comprise only 30% of this southern Malawi population. Young adults were the second largest contributors, while U5s and adults over 30 were each responsible for

Prompt and effective treatment is key to malaria control and prevention, as it reduces disease morbidity and mortality and minimizes the number of transmission reservoirs. Transmission reduction may be particularly important among school-age children (SAC, 5-15 years old), who have the highest prevalence of Plasmodium falciparum infection in southern Malawi. We hypothesized that one factor contributing to this difference in prevalence is that SAC are less likely to seek appropriate treatment for fever than children younger than 5 years. In this study, we assessed treatment-seeking behaviors of people of all ages between 2012 and 2014 in Malawi. During each of the five cross-sectional surveys, all members of ∼900 households reported on fever and treatment-seeking in the previous 2 weeks. Multilevel logistic regression was used to analyze predictors of whether febrile people sought treatment and whether they did so at formal (government/private clinics) or informal sources (primarily shops). Twenty-two percent of participants (3,579/16,621) reported fever, and 2,715 of those (75.9%) sought treatment. Seeking treatment exclusively from local shops remains a common practice, although use of recommended diagnostic testing and antimalarial drugs was infrequently reported there. Although SAC were not significantly less likely than children aged < 5 years to seek treatment, SAC and adults (age ≥ 16 years) were significantly less likely to use formal sources. Our results indicate that encouraging treatment at government/private clinics and increasing retail access to appropriate antimalarial testing and treatment, especially among SAC, could help remedy inadequate treatment of symptomatic disease and potentially reduce Plasmodium transmission in Malawi.

Background Respiratory syncytial virus (RSV) is an established cause of serious lower respiratory disease in children, but the burden in adults is less well studied. Methods We conducted a retrospective study of hospitalizations among adults ≥20 years from the 1997–2012 National Inpatient Sample. Trends in RSV admissions were described relative to unspecified viral pneumonia admissions. Hospitalization severity indicators were compared among immunocompromised RSV, non-immunocompromised RSV, and influenza admissions. Results An estimated 28237 adult RSV hospitalizations occurred, compared with 652818 influenza hospitalizations; 34% were immunocompromised individuals. Respiratory syncytial virus and influenza patients had similar age, gender, and race distributions, but RSV was more often diagnosed in urban teaching hospitals (73.0% for RSV vs 34.6% for influenza) and large hospitals (71.9% vs 56.4%). Respiratory syncytial virus hospitalization rates increased from 1997 to 2012, particularly for those ≥60, increasing from 0.5 to 4.6 per 100000, whereas unspecified pneumonia admission rates decreased significantly (P < .001). Immunocompromised patients with RSV hospitalization had significantly higher inpatient mortality (P = .013), use of mechanical ventilation (P = .016), mean length of stay (LOS) (P < .001), and mean cost (P < .001) than non-immunocompromised RSV hospitalizations. Overall, RSV hospitalizations were more severe than influenza hospitalizations (6.2% mortality for RSV vs 3.0% for influenza, 16.7% vs 7.2% mechanical ventilation, mean LOS of 6.0 vs 3.6 days, and mean cost of $38828 vs $14519). Conclusions Respiratory syncytial virus hospitalizations in adults are increasing, likely due to increasing recognition and diagnosis. The burden of RSV in adults deserves attention. Although there are fewer hospitalizations than influenza, those that are diagnosed are on average more severe.

Background In endemic areas, many people experience asymptomatic Plasmodium infections, particularly older children and adults, but their transmission contribution is unknown. Though not the exclusive determinant of infectiousness, transmission from humans to mosquitoes requires blood meals containing gametocytes. Gametocytes often occur at submicroscopic densities, challenging measurement in human populations. More sensitive molecular techniques allow better characterization of gametocyte epidemiologic patterns. Methods Approximately 30 households were selected from each of eight sites in southern Malawi during two cross-sectional surveys. Blood was sampled from 623 people during the dry season and 896 the following rainy season. Among people PCR-positive for Plasmodium falciparum, mature gametocytes were detected by qRT-PCR. Regression models evaluated predictors of gametocyte carriage and density in the total population and among those with PCR-positive infections. Results The prevalence of gametocyte carriage by molecular testing was 3.5% during the dry season and 8.6% during the rainy season, and by microscopy 0.8 and 3.3%, respectively. Nearly half of PCR-positive infections carried gametocytes, regardless of recent symptom status. Among P. falciparum-infected people, only living in unfinished houses and age were significantly associated with gametocyte presence. Infected people in unfinished houses had higher odds of carrying gametocytes (OR 2.24, 95% CI 1.16–4.31), and 31% (95% CI 3–65%) higher gametocyte density than those in finished houses. School-age children (5–15 years), had higher odds than adults (≥16 years) of having gametocytes when infected (OR 2.77, 95% CI 1.47–5.19), but 31% (95% CI 11–47%) lower gametocyte density. Children

BACKGROUND:Respiratory syncytial virus (RSV) causes significant pediatric morbidity and is the most common cause of bronchiolitis. Bronchiolitis hospitalizations declined among US infants from 2000‒2009; however, rates in infants at high risk for RSV have not been described. This study examined RSV and unspecified bronchiolitis (UB) hospitalization rates from 1997‒2012 among US high-risk infants. METHODS:The Kids' Inpatient Database (KID) infant annual RSV (ICD-9 079.6, 466.11, 480.1) and UB (ICD-9 466.19, 466.1) hospitalization rates were estimated using weighted counts. Denominators were based on birth hospitalizations with conditions associated with high-risk for RSV: chronic perinatal respiratory disease (chronic lung disease [CLD]); congenital airway anomalies (CAA); congenital heart disease (CHD); Down syndrome (DS); and other genetic, metabolic, musculoskeletal, and immunodeficiency conditions. Preterm infants could not be identified. Hospitalizations were characterized by mechanical ventilation, inpatient mortality, length of stay, and total cost (2015$). Poisson and linear regression were used to test statistical significance of trends. RESULTS:RSV and UB hospitalization rates were substantially elevated for infants with higher-risk CHD, CLD, CAA and DS without CHD compared with all infants. RSV rates declined by 47.0% in CLD and 49.7% in higher-risk CHD infants; no other declines in high-risk groups were observed. UB rates increased in all high-risk groups except for a 22.5% decrease among higher-risk CHD. Among high-risk infants, mechanical ventilation increased through 2012 to 20.4% and 13.5% of RSV and UB hospitalizations; geometric mean cost increased to $31,742 and $25,962, respectively, and RSV mortality declined to 0.9%. CONCLUSIONS:Among high-risk infants between 1997 and 2012, RSV hospitalization rates declined among CLD and higher-risk CHD infants, coincident with widespread RSV immunoprophylaxis use in these populations. UB hospitalization rates increased in all high-risk groups except higher-risk CHD, suggesting improvement in the health status of higher-risk CHD infants, potentially due to enhanced surgical interventions. Mechanical ventilation use and RSV and UB hospitalization costs increased while RSV mortality declined.

The epidemiology of immune thrombocytopenic purpura (ITP) is not well-characterised in the general population. This study described the incidence and survival of ITP using the UK population-based General Practice Research Database (GPRD). ITP patients first diagnosed in 1990-2005 were identified in the GPRD. Overall incidence rates (per 100,000 person-years) and rates by age, sex, and calendar periods were calculated. Survival analysis was conducted using the Kaplan-Meier and proportional hazard methods. A total of 1145 incident ITP patients were identified. The crude incidence was 3.9 (95% confidence interval [CI]: 3.7-4.1). Overall average incidence was statistically significantly higher in women (4.4, 95% CI: 4.1-4.7) compared to men (3.4; 95% CI: 3.1-3.7). Among men, incidence was bimodal with peaks among ages under 18 and between 75-84 years. The hazard ratio for death among ITP patients was 1.6 (95% CI: 1.3-1.9) compared to age- and sex-matched comparisons. During follow-up 139 cases died, of whom 75 had a computerised plausible cause of death. Death was related to bleeding in 13% and infection in 19% of these 75. In conclusion, ITP incidence varies with age and is higher in women than men. This potentially serious medical condition is associated with increased mortality in the UK.

Malaria surveillance and interventions in endemic countries often target young children at highest risk of malaria morbidity and mortality. We aimed to determine whether school-age children and adults not captured in surveillance serve as a reservoir for malaria infection and may contribute to malaria transmission. Cross-sectional surveys were conducted in one rainy and one dry season in southern Malawi. Demographic and health information was collected for all household members. Blood samples were obtained for microscopic and PCR identification of Plasmodium falciparum. Among 5796 individuals aged greater than six months, PCR prevalence of malaria infection was 5%, 10%, and 20% in dry, and 9%, 15%, and 32% in rainy seasons in Blantyre, Thyolo, and Chikhwawa, respectively. Over 88% of those infected were asymptomatic. Participants aged 6–15 years were at higher risk of infection (OR=4.8; 95%CI, 4.0–5.8) and asymptomatic infection (OR=4.2; 95%CI, 2.7–6.6) than younger children in all settings. School-age children used bednets less frequently than other age groups. Compared to young children, school-age children were brought less often for treatment and more often to unreliable treatment sources. Conclusion: School-age children represent an underappreciated reservoir of malaria infection and have less exposure to antimalarial interventions. Malaria control and elimination strategies may need to expand to include this age group.

Background Recent data from Malawi suggest that school-aged children (SAC), aged 5–15 years, have the highest prevalence of Plasmodium falciparum infection among all age groups. They are the least likely group to utilize insecticide-treated nets (ITNs), the most commonly available intervention to prevent malaria in Africa. This study examined the effects of a universal ITN distribution campaign, and their durability over time in SAC in Malawi. This study identified factors that influence net usage among SAC and how these factors changed over time. Methods Cross-sectional surveys using cluster random sampling were conducted at the end of each rainy and dry season in southern Malawi from 2012 to 2014; six surveys were done in total. Mass net distribution occurred between the first and second surveys. Data were collected on household and individual net usage as well as demographic information. Statistical analyses used generalized linear mixed models to account for clustering at the household and neighbourhood level. Results There were 7347 observations from SAC and 14,785 from young children and adults. SAC used nets significantly less frequently than the rest of the population (odds ratio (OR) from 0.14 to 0.38). The most important predictors of net usage among SAC were a lower ratio of people to nets in a household and higher proportion of nets that were hanging at the time of survey. Older SAC (11–15 years) were significantly less likely to use nets than younger SAC (5–10 years) [OR = 0.24 (95 % CI: 0.21, 0.28)]. The universal bed net campaign led to a statistically significant population-wide increase in net use, however net use returned to near baseline within 3 years. Conclusions This study suggests that a single universal net distribution campaign, in combination with routine distribution through health clinics is not sufficient to cause a sustained increase in net usage among SAC. Novel approaches to ITN distribution, such as school-based distribution, may be needed to address the high prevalence of infection in SAC.

Background After increasing coverage of malaria interventions, malaria prevalence remains high in Malawi. Previous studies focus on the impact of malaria interventions among children under 5 years old. However, in Malawi, the prevalence of infection is highest in school-aged children (SAC), ages 5 to 15 years. This study examined the interaction between age group and insecticide-treated net (ITN) use for preventing individual and community-level infection in Malawi. Methods Six cross-sectional surveys were conducted in the rainy and dry seasons in southern Malawi from 2012 to 2014. Data were collected on household ITN usage and demographics. Blood samples for detection of Plasmodium falciparum infection were obtained from all household members present and over 6 months of age. Generalized linear mixed models were used to account for clustering at the household and community level. Results There were 17,538 observations from six surveys. The association between ITN use and infection varied by season in SAC, but not in other age groups. The adjusted odds ratio (OR) for infection comparing ITN users to non-users among SAC in the rainy season and dry season was 0.78 (95% CI 0.56, 1.10) and 0.51 (0.35, 0.74), respectively. The effect of ITN use did not differ between children under five and adults. Among all non-SACs the OR for infection was 0.78 (0.64, 0.95) in those who used ITNs compared to those that did not. Community net use did not protect against infection. Conclusions Protection against infection with ITN use varies by age group and season. Individual estimates of protection are moderate and a community-level effect was not detected. Additional interventions to decrease malaria prevalence are needed in Malawi. Electronic supplementary material The online version of this article (doi:10.1186/s12936-017-1686-2) contains supplementary material, which is available to authorized users.