11 research outputs found
Distribution of influenza virus types by age using case-based global surveillance data from twenty-nine countries, 1999-2014
Background: Influenza disease burden varies by age and this has important public health implications. We compared the proportional distribution of different influenza virus types within age strata using surveillance data from twenty-nine countries during 1999-2014 (N=358,796 influenza cases)
Temporal Patterns of Influenza A and B in Tropical and Temperate Countries: What Are the Lessons for Influenza Vaccination?
<div><p>Introduction</p><p>Determining the optimal time to vaccinate is important for influenza vaccination programmes. Here, we assessed the temporal characteristics of influenza epidemics in the Northern and Southern hemispheres and in the tropics, and discuss their implications for vaccination programmes.</p><p>Methods</p><p>This was a retrospective analysis of surveillance data between 2000 and 2014 from the Global Influenza B Study database. The seasonal peak of influenza was defined as the week with the most reported cases (overall, A, and B) in the season. The duration of seasonal activity was assessed using the maximum proportion of influenza cases during three consecutive months and the minimum number of months with ≥80% of cases in the season. We also assessed whether co-circulation of A and B virus types affected the duration of influenza epidemics.</p><p>Results</p><p>212 influenza seasons and 571,907 cases were included from 30 countries. In tropical countries, the seasonal influenza activity lasted longer and the peaks of influenza A and B coincided less frequently than in temperate countries. Temporal characteristics of influenza epidemics were heterogeneous in the tropics, with distinct seasonal epidemics observed only in some countries. Seasons with co-circulation of influenza A and B were longer than influenza A seasons, especially in the tropics.</p><p>Discussion</p><p>Our findings show that influenza seasonality is less well defined in the tropics than in temperate regions. This has important implications for vaccination programmes in these countries. High-quality influenza surveillance systems are needed in the tropics to enable decisions about when to vaccinate.</p></div
Distribution of influenza virus types by age using case-based global surveillance data from twenty-nine countries, 1999-2014
BACKGROUND : Influenza disease burden varies by age and this has important public health implications. We
compared the proportional distribution of different influenza virus types within age strata using surveillance data
from twenty-nine countries during 1999-2014 (N=358,796 influenza cases).
METHODS : For each virus, we calculated a Relative Illness Ratio (defined as the ratio of the percentage of cases in an
age group to the percentage of the country population in the same age group) for young children (0-4 years),
older children (5-17 years), young adults (18-39 years), older adults (40-64 years), and the elderly (65+ years). We
used random-effects meta-analysis models to obtain summary relative illness ratios (sRIRs), and conducted metaregression
and sub-group analyses to explore causes of between-estimates heterogeneity.
RESULTS : The influenza virus with highest sRIR was A(H1N1) for young children, B for older children, A(H1N1)
pdm2009 for adults, and (A(H3N2) for the elderly. As expected, considering the diverse nature of the national
surveillance datasets included in our analysis, between-estimates heterogeneity was high (I2>90%) for most sRIRs.
The variations of countries’ geographic, demographic and economic characteristics and the proportion of
outpatients among reported influenza cases explained only part of the heterogeneity, suggesting that multiple
factors were at play.
CONCLUSIONS : These results highlight the importance of presenting burden of disease estimates by age group and
virus (sub)type.Table S1. Number of influenza cases caused by the
difference influenza viruses that were included in the analysis. The Global
Influenza B Study, 1999-2014.Figure S1. Forest plot of the Relative Illness Ratio for
patients aged 0-4 years infected with A(H1N1) influenza virus. The Global
Influenza B Study, 1999-2014. Figure S2. Forest plot of the Relative Illness
Ratio for patients aged 5-17 years infected with A(H1N1) influenza virus.
The Global Influenza B Study, 1999-2014. Figure S3. Forest plot of the
Relative Illness Ratio for patients aged 18-39 years infected with A(H1N1)
influenza virus. The Global Influenza B Study, 1999-2014. Figure S4. Forest
plot of the Relative Illness Ratio for patients aged 40-64 years infected
with A(H1N1) influenza virus. The Global Influenza B Study, 1999-2014.
Figure S5. Forest plot of the Relative Illness Ratio for patients aged 65+
years infected with A(H1N1) influenza virus. The Global Influenza B Study,
1999-2014.Table S2. Summary Relative Illness Ratio (sRIR), 95%
confidence intervals (95% CI) across age groups and influenza viruses by
categories of country ageing index. The Global Influenza B Study, 1999-
2014. Table S3. Summary Relative Illness Ratio (sRIR), 95% confidence
intervals (95% CI) across age groups and influenza viruses by percentage
of outpatients among cases reported to the influenza surveillance system.
The Global Influenza B Study, 1999-2014. Table S4. Summary Relative
Illness Ratio (sRIR), 95% confidence intervals (95% CI) across age groups
and influenza viruses by country latitude. The Global Influenza B Study,
1999-2014. Table S5. Summary Relative Illness Ratio (sRIR), 95%
confidence intervals (95% CI) across age groups and influenza viruses by
percentage of influenza cases caused by that influenza virus in the same
season. The Global Influenza B Study, 1999-2014. Table S6. Summary
Relative Illness Ratio (sRIR), 95% confidence intervals (95% CI) across age
groups and influenza viruses by percentage of influenza cases caused by
that influenza virus in the previous season. The Global Influenza B Study, 1999-2014. Table S7. Summary Relative Illness Ratio (sRIR), 95%
confidence intervals (95% CI) across age groups and influenza viruses
by categories of country gross domestic product (GDP) per capita. The
Global Influenza B Study, 1999-2014.The Global Influenza B Study is funded by an unrestricted research grant
from Sanofi Pasteur.https://bmcinfectdis.biomedcentral.comam2019Medical Virolog
Influenza cases reported to the national influenza surveillance system by each participating country (from southern- to northern-most) and percentages of cases due to influenza type B virus.
<p>Influenza cases reported to the national influenza surveillance system by each participating country (from southern- to northern-most) and percentages of cases due to influenza type B virus.</p
Median percentage of influenza cases that occurred during the 3-month peak period and median number of months to have ≥80% of influenza cases during a season in countries of the Southern hemisphere, the inter-tropical belt, and the Northern hemisphere.
<p>Median percentage of influenza cases that occurred during the 3-month peak period and median number of months to have ≥80% of influenza cases during a season in countries of the Southern hemisphere, the inter-tropical belt, and the Northern hemisphere.</p
Mean percentage of influenza cases by month (black diamonds) and number of times the peak of the influenza season took place in each month (pink squares) for countries of Northern hemisphere.
<p>Mean percentage of influenza cases by month (black diamonds) and number of times the peak of the influenza season took place in each month (pink squares) for countries of Northern hemisphere.</p
Mean percentage of influenza cases by month (black diamonds) and number of times the peak of the influenza season took place in each month (pink squares) for countries in the inter-tropical belt.
<p>Mean percentage of influenza cases by month (black diamonds) and number of times the peak of the influenza season took place in each month (pink squares) for countries in the inter-tropical belt.</p
Mean percentage of influenza cases by month (black diamonds) and number of times the peak of the influenza season took place in each month (pink squares) for countries in the Southern hemisphere.
<p>Mean percentage of influenza cases by month (black diamonds) and number of times the peak of the influenza season took place in each month (pink squares) for countries in the Southern hemisphere.</p
Median percentage of influenza cases that occurred during the 3-month peak period and median number of months to have ≥80% of influenza cases during a season by zone (Southern hemisphere, inter-tropical belt, Northern hemisphere) and proportion of influenza B.
<p>Median percentage of influenza cases that occurred during the 3-month peak period and median number of months to have ≥80% of influenza cases during a season by zone (Southern hemisphere, inter-tropical belt, Northern hemisphere) and proportion of influenza B.</p