Modelling the Force of Infection for Hepatitis A in an Urban Population-Based Survey: A Comparison of Transmission Patterns in Brazilian Macro-Regions

Abstract

BackgroundThis study aimed to identify the transmission pattern of hepatitis A (HA) infection based on a primary dataset from the Brazilian National Hepatitis Survey in a pre-vaccination context. The national survey conducted in urban areas disclosed two epidemiological scenarios with low and intermediate HA endemicity.MethodsA catalytic model of HA transmission was built based on a national seroprevalence survey (2005 to 2009). The seroprevalence data from 7,062 individuals aged 5–69 years from all the Brazilian macro-regions were included. We built up three models: fully homogeneous mixing model, with constant contact pattern; the highly assortative model and the highly assortative model with the additional component accounting for contacts with infected food/water. Curves of prevalence, force of infection (FOI) and the number of new infections with 99% confidence intervals (CIs) were compared between the intermediate (North, Northeast, Midwest and Federal District) and low (South and Southeast) endemicity areas. A contour plot was also constructed.ResultsThe anti- HAV IgG seroprevalence was 68.8% (95% CI, 64.8%–72.5%) and 33.7% (95% CI, 32.4%–35.1%) for the intermediate and low endemicity areas, respectively, according to the field data analysis. The models showed that a higher force of infection was identified in the 10- to 19-year-old age cohort (∼9,000 infected individuals per year per 100,000 susceptible persons) in the intermediate endemicity area, whereas a higher force of infection occurred in the 15- to 29-year-old age cohort (∼6,000 infected individuals per year per 100,000 susceptible persons) for the other macro-regions.ConclusionOur findings support the shift of Brazil toward intermediate and low endemicity levels with the shift of the risk of infection to older age groups. These estimates of HA force of infection stratified by age and endemicity levels are useful information to characterize the pre-vaccination scenario in Brazil.

Hepatitis A seroprevalence in public school children in Campos dos Goytacazes, Rio de Janeiro State, Brazil, prior to the introduction of the hepatitis A universal childhood vaccination

“…Indeed, while Brazil was formerly recognized as an endemic country for hepatitis A, it is now presenting two distinct epidemiological patterns: intermediate endemicity of hepatitis A in the North, Northeast and Central regions, and low endemicity in the South and Southeast regions 14,15,16 . Recently, force of infection of estimates of hepatitis A stratified by age and endemicity levels based on a primary dataset from the Brazilian National Hepatitis Survey also showed that there is a shift of risk of HAV infection to older age groups 17 . This transition in the epidemiological pattern can be worrisome, since the delay in the age of exposure does not subsequently eliminate the risk of infection.…”

Force of infection of Middle East respiratory syndrome in dromedary camels in Kenya

“…There are a few possible reasons why this FOI analysis identified the oldest age group as having the highest risk of infection based on model AIC. Questions remain as to whether [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]. Furthermore, the oldest age group has a much larger age range than the others, and therefore represents a greater cumulative risk.…”

“…To our knowledge, this is the first study to investigate FOI for MERS-CoV in dromedary camels. FOI can also be used to estimate the reproductive number of the pathogen in a population (the average number of secondary infections resulting from the introduction of an infectious individual into a completely susceptible population) [20,21], and as a parameter in disease transmission models [22]. Improving our understanding of MERS-CoV dynamics in camels raised outside of the Middle East will contribute towards a greater understanding of the virus in the reservoir host, and may provide points of comparison for viral dynamics in camels in the Middle East where zoonotic transmission is ongoing.…”

A Rare Case of Transfusion Transmission of Hepatitis A Virus to Two Patients with Haematological Disease

“…In Brazil, two epidemiological scenarios with low and intermediate HAV endemicity are shown. The anti-HAV IgG seroprevalence varies from 33.7% to 68.8%, for the intermediate and low endemic areas [2]. HAV is a non-enveloped single-stranded RNA picornavirus of the genus Hepatovirus whose most common genotypes found in human infections are the genotypes I and III [1,2,3,4].…”