Influenza activity in Kenya, 2007–2013: timing, association with climatic factors, and implications for vaccination campaigns

Abstract

BackgroundInformation on the timing of influenza circulation remains scarce in Tropical regions of Africa.ObjectivesWe assessed the relationship between influenza activity and several meteorological factors (temperature, specific humidity, precipitation) and characterized the timing of influenza circulation and its implications to vaccination strategies in Kenya.MethodsWe analyzed virologically confirmed influenza data for outpatient influenza‐like illness (ILI), hospitalized for severe acute respiratory infections (SARI), and cases of severe pneumonia over the period 2007–2013. Using logistic and negative binomial regression methods, we assessed the independent association between climatic variables (lagged up to 4 weeks) and influenza activity.ResultsThere were multiple influenza epidemics occurring each year and lasting a median duration of 2–4 months. On average, there were two epidemics occurring each year in most of the regions in Kenya, with the first epidemic occurring between the months of February and March and the second one between July and November. Specific humidity was independently and negatively associated with influenza activity. Combinations of low temperature (<18°C) and low specific humidity (<11 g/kg) were significantly associated with increased influenza activity.ConclusionsOur study broadens understanding of the relationships between seasonal influenza activity and meteorological factors in the Kenyan context. While rainfall is frequently thought to be associated with influenza circulation in the tropics, the present findings suggest low humidity is more important in Kenya. If annual vaccination were a component of a vaccination strategy in Kenya, the months of April to June are proposed as optimal for associated campaigns.

Continuous Invasion by Respiratory Viruses Observed in Rural Households During a Respiratory Syncytial Virus Seasonal Outbreak in Coastal Kenya

“…Some of the pathogens were uncommon, and it is likely that a seasonal peak of some viruses fell outside the study period. In this location, peak occurrence of influenza (A or B) is in the second half of each year based on inpatient pediatric surveillance [17,18]. HMPV circulated prior to the start of RSV season, as shown from corresponding hospital data ( Supplementary Figure 1), unlike previous studies reporting co-circulation with RSV [19].…”

Effect of meteorological factors on the activity of influenza in Chongqing, China, 2012–2019

“…Where E(Yt) is the expected weekly con rmed in uenza cases every ten thousand outpatient visits on week t; α is the intercept; cb( ) represents the cross-basis matrix of climate factors, including mean temperature, relative humidity, aggregate rainfall, wind speed and sunshine; df is the degree of freedom; X j is the other explanatory variables of meteorological factors; time refers to duration of seasonality and long-term trend; holiday is an indicator variable which equals to 1 if week t is in school holidays and 0 otherwise. We used Akaike Information criterion (AIC) to choose the df, which was supported by other references [10][11][12][13] . The weeks of lag structure in the models were determined by incubation period and infectious period of in uenza virus 14 , the Akaike Information criteria and other references 10,11 .…”

“…We used Akaike Information criterion (AIC) to choose the df, which was supported by other references [10][11][12][13] . The weeks of lag structure in the models were determined by incubation period and infectious period of in uenza virus 14 , the Akaike Information criteria and other references 10,11 . We provided all AICs in the appendix (Supplementary Tab.…”

“…Previous studies have inconsistent ndings on the association between rainfall and in uenza. Many studies reported increased in uenza circulation during the rainy seasons 28,29 , while others reported no or contradicting effects of rainfall 11,30 . The ndings of our study agrees with the former.…”

Building laboratory capacity to detect and characterize pathogens of public and global health security concern in Kenya

“…Between 2014 and 2017, DSLP provided laboratory support for two observational rotavirus vaccine studies: Rotavirus-Vaccine Impact on Diarrhea in Africa (R-VIDA), a multi-country study that includes Kenya, Mali and Gambia; and Rotavirus Immunization Program Evaluation in Kenya ((RIPEK), a multi-site study within Kenya) to determine the effectiveness of the rotavirus vaccine. Recent influenza studies in Kenya that were supported by DLSP assisted in describing influenza disease burden in the country which was crucial information used by the Kenyan National Immunization Technical Advisory Group (KENITAG) for the recommendation of influenza vaccination for children ages 6-23 months [13][14][15]. In addition, this diagnostic capacity enabled other complex clinical research projects including Pediatric Respiratory Etiology Surveillance Study (PRESS) and Child Health and Mortality Prevention Surveillance (CHAMPS) that collect data to describe the causes of under-five child mortality in high-mortality settings [16].…”