Ansaldi F, Marensi L, Puppo S, Rosselli R, Turello V, Zoppi G, Carloni R, Oreste P, Riente R, Valle L, Orsi A, Sticchi L, Durando P, Icardi G
Department of Health Sciences, University of Genoa, Italy.
J Prev Med Hyg. 2007 Sep;48(3):103-8.
Hepatitis A remains an important public health problem in low endemicity areas, because of the social and economic high burden of cyclical outbreaks. In this study we described an outbreak of HAV infection occurred in the city of Genoa and in its proximity and the viral circulation in the post-epidemic period. In order to identify risk factors associated to the illness and to determine the source of infection and the dynamics of virus evolution, we conducted an epidemiological and molecular investigation by a case-control study and by sequence analysis of high variable regions of the genome.
From May to October 2005, 58 HAV hepatitis cases were notified. The case-control study showed that beach establishment attending is strongly associated with HAV hepatitis (OR = 24.5, p-value < 0.01), at multivariate analysis. The profile of epidemic curve, the clinical onset of primary cases who occurred in few weeks and the geographic distribution of cases clearly indicated a common exposure to a point source: the outbreak can be probably associated with a contaminated food product dispensed in the affected area. The outbreak has been mainly caused by a single variant, confirming the common exposure to a point source; this variant previously circulated within homosexual man (MSM) network in Northern Europe. During the outbreak and in the following months, different variants originating from Southeast Asia, Southern America and Northern Africa, have co-circulated: all these cases were related to international travel and none of these had determined secondary cases.
The epidemiological picture of hepatitis A in Liguria is characterized by a wide heterogeneity of circulating HAV strains. This pattern could be associated with the increase of imported cases and transmission within network of persons with similar risk factors. Molecular approach coupled to descriptive and analytical epidemiological studies appeared un-replaceable tools for management and control of HAV outbreaks, because of their capacity to recognize infection origin, transmission patterns and dynamics of virus evolution.
由于周期性疫情造成的社会和经济负担沉重，甲型肝炎在低流行地区仍是一个重要的公共卫生问题。在本研究中，我们描述了在热那亚市及其周边地区发生的甲型肝炎病毒（HAV）感染疫情以及疫情后期的病毒传播情况。为了确定与该疾病相关的危险因素，确定感染源以及病毒进化动态，我们通过病例对照研究以及对基因组高变区进行序列分析开展了一项流行病学和分子学调查。
2005年5月至10月，共报告了58例甲型肝炎病例。病例对照研究表明，多因素分析显示，光顾海滩设施与甲型肝炎密切相关（比值比=24.5，p值<0.01）。疫情曲线特征、数周内出现的首例病例的临床发病情况以及病例的地理分布清楚地表明存在共同暴露于一个点源的情况：此次疫情可能与受影响地区分发的一种受污染食品有关。此次疫情主要由单一变异株引起，证实存在共同暴露于一个点源的情况；该变异株此前在北欧的男男性行为者（MSM）网络中传播。在疫情期间及之后的几个月里，源自东南亚、南美和北非的不同变异株共同传播：所有这些病例均与国际旅行有关，且均未导致二代病例。
利古里亚地区甲型肝炎的流行病学情况特点是循环的甲型肝炎病毒株具有广泛的异质性。这种模式可能与输入性病例增加以及具有相似危险因素的人群网络内传播有关。由于能够识别感染源、传播模式和病毒进化动态，分子方法与描述性和分析性流行病学研究相结合似乎是管理和控制甲型肝炎疫情不可替代的工具。
