Van der Stuyft P, Gianella A, Pirard M, Cespedes J, Lora J, Peredo C, Pelegrino J L, Vorndam V, Boelaert M
Institute of Tropical Medicine, Epidemiology Unit, Antwerp, Belgium.
Lancet. 1999 May 8;353(9164):1558-62. doi: 10.1016/s0140-6736(99)03291-2.
Reinvasion by Aedes aegypti of cities in the Americas poses a threat of urbanisation of yellow fever. After detection of yellow-fever infection in a resident of the city of Santa Cruz, Bolivia, in December, 1997, we investigated all subsequent suspected cases.
We introduced active surveillance of yellow fever in the Santa Cruz area. Hospitals and selected urban and rural health centres reported all suspected cases. Patients were serologically screened for yellow fever, dengue, hepatitis A and B, and leptospirosis. We collected clinical and epidemiological information from patients' records and through interviews. We also carried out a population-based serosurvey in the neighbourhood of one case.
Between December, 1997, and June, 1998, symptomatic yellow-fever infection was confirmed in six residents of Santa Cruz, five of whom died. Five lived in the southern sector of the city. Two had not left the city during the incubation period, and one had visited only an area in which sylvatic transmission was deemed impossible. Of the 281 people covered in the serosurvey 16 (6%) were positive for IgM antibody to yellow fever. Among five people for whom this result could not be explained by recent vaccination, there were two pairs of neighbours.
Urban transmission of yellow fever in Santa Cruz was limited in space and time. Low yellow-fever immunisation coverage and high infestation with A. aegypti in the city, and the existence of endemic areas in the region present a risk for future urban outbreaks. We recommend immediate large-scale immunisation of the urban population, as well as tightened surveillance and appropriate vector control.
美洲城市中埃及伊蚊的再次入侵对黄热病的城市化构成威胁。1997年12月在玻利维亚圣克鲁斯市一名居民中检测到黄热病感染后，我们对所有随后的疑似病例进行了调查。
我们在圣克鲁斯地区引入了黄热病主动监测。医院以及选定的城乡卫生中心报告所有疑似病例。对患者进行黄热病、登革热、甲型和乙型肝炎以及钩端螺旋体病的血清学筛查。我们从患者记录中并通过访谈收集临床和流行病学信息。我们还在一例病例所在社区开展了基于人群的血清学调查。
1997年12月至1998年6月期间，圣克鲁斯的6名居民被确诊有症状性黄热病感染，其中5人死亡。5人居住在该市南部地区。2人在潜伏期内未离开该市，1人仅去过一个被认为不可能发生丛林传播的地区。在血清学调查涵盖的281人中，16人（6%）黄热病IgM抗体呈阳性。在5名近期接种疫苗无法解释该结果的人中，有两对是邻居。
圣克鲁斯黄热病的城市传播在空间和时间上有限。该市黄热病免疫接种覆盖率低、埃及伊蚊大量滋生，且该地区存在地方性流行区，这对未来城市疫情爆发构成风险。我们建议立即对城市人口进行大规模免疫接种，同时加强监测并采取适当的病媒控制措施。
