The age of infection with varicella-zoster virus in St Lucia, West Indies

Abstract

SUMMARYSera from an age-stratified sample of 1810 people from the Caribbean island of St Lucia were tested for antibodies against varicella-zoster virus. The results indicate that very few infections occur in childhood, which agrees with clinical survey data from other tropical countries, but contrasts with the observed high case rate in children in temperate countries. The alternative hypotheses which may explain these results are discussed, and it is suggested that high ambient temperatures interfere with the transmission of the virus. Irrespective of the cause, the pattern of varicella incidence observed has important implications for any vaccination policy adopted in tropical countries. INTROD)UCTIONVaricella (chickenpox), primary infection with varicella zoster virus (VZV), is a very common childhood infection in temperate countries, although the mean age of infection is significantly higher in developing countries [1][2][3][4][5][6][7][8]. This is the reverse of the age pattern observed with many other directly transmitted infections, such as measles, where the mean age of infection is typically low in developing or tropical countries because of a mixture of high population densities, which provide more opportunities for disease transmission, and high birth rates, which provide a large pool of young susceptibles [9]. The reversed age pattern of varicella infection raises questions about the nature of varicella transmission.In order to address these questions this paper discusses the evidence that the force of infection (the per capita rate at which susceptibles acquire infection) of VZV is less in tropical than in temperate countries. The paper examines published reports, describes a serological investigation of the pattern of infection in the population of the Caribbean island of St Lucia and uses the survey data to estimate the age-specific force of infection.The discussion of varicella transmission in this paper centres on differences between tropical and temperate countries. However, tropical countries are usually

Soroepidemiology of Varicella in Brazil - results of a prospective cross-sectional study

“…No Brasil e na maioria dos outros países latinoamericanos existem somente dados empíricos sobre a epidemiologia da varicela, prevalência de anticorpos anti-VZV na população e sobre surtos da doença 15,16,22,23 . Esta escassez de dados, associada à disponibilidade de uma vacina efetiva, estimularam o início deste estudo soroepidemiológico, prospectivo, transversal e baseado na população.…”

“…Esses dados não foram distorcidos por idade e sexo. Esses resultados não eram esperados se considerarmos os relatos sugerindo que a combinação da temperatura ambiental com a umidade pode inativar o vírus e reduzir sua transmissão nos trópicos 7,10,23,24 . Se a temperatura é responsável por uma diminuição na transmissão da varicela deveríamos esperar uma maior ocorrência de casos da doença em épocas de menor temperatura nos países tropicais.…”

Microbiology laboratory and the management of mother-child varicella-zoster virus infection

“…Epidemiology is different in tropical countries, where there is no marked seasonality [5] . The infection is acquired in childhood less than in temperate countries, with only 25%-85% of subjects contracting primary infection before the age of 15 years [122][123][124][125][126][127][128][129][130][131] . Various hypotheses have been postulated to explain this difference, including viral inactivation due to high ambient temperatures, race, interference from other more prevalent viruses and a lack of exposure due to the rural living conditions in the tropics, where VZV does not circulate very much [123,[132][133][134] .…”

“…The infection is acquired in childhood less than in temperate countries, with only 25%-85% of subjects contracting primary infection before the age of 15 years [122][123][124][125][126][127][128][129][130][131] . Various hypotheses have been postulated to explain this difference, including viral inactivation due to high ambient temperatures, race, interference from other more prevalent viruses and a lack of exposure due to the rural living conditions in the tropics, where VZV does not circulate very much [123,[132][133][134] . Advanced age of infection and the severity of adult disease may be responsible for the increased morbidity and mortality due to varicella and complications in these areas [59,[135][136][137] .…”

“…However, a reported history of varicella is rather less predictive in women from tropical countries where the seroprevalence rate is lower [123,[129][130][131][132]134,150,300,[322][323][324] ( Table 2). The intense population movements of recent times should encourage a careful evaluation of the epidemiology of a woman's region of origin.…”