Vector densities that potentiate dengue outbreaks in a Brazilian city.

To identify the critical vector density that potentiates dengue outbreaks in an endemic site and to identify obstacles to anti-dengue activities, we correlated a series of dengue outbreaks in a Brazilian city with the intensity of its anti-vector source-reduction activities. The proportion of houses infested by vector mosquitoes correlated inversely with intensity of anti-mosquito interventions, and the vector population developed independently of rainfall. Local periods of drought promoted vector abundance in two ways: residents stored water in which vector mosquitoes could breed, and cholera outbreaks due to contaminated water diverted local health workers from routine anti-vector activities. One dengue outbreak became apparent to authorities more than two months after it commenced but would have been identified almost immediately had dengue-like disease in indicator hospitals been monitored. Active surveillance, therefore, offers a window of opportunity for promptly executed anti-dengue interventions. Source-reduction measures that suppress vector infestations to less than 1% of houses effectively avert outbreaks of dengue.

[Surveillance and active search of suspected cases of hemorrhagic dengue in Ribeirão Preto, São Paulo]. / Vigilância e busca ativa de casos suspeitos de dengue hemorrágico em Ribeirão Preto, São Paulo.

A clinical-epidemiological case study was carried out to evaluate a surveillance and active search system for suspect cases of dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS) during a dengue epidemic in the Ribeirão Preto municipality, State of São Paulo, Brazil, between November 1990 and March 199. This was the first dengue epidemic ever recorded in this region. Although dengue is a growing public health problem in Brazil, and DHF/DSS has been reported to be evolving in the Americas, health officials have shown a passive attitude towards the disease, partly due to lack of experience. Reporting dengue occurrences, both of isolated cases and of epidemics, is essential to reduce mortality. The data analyzed were collected through the official epidemiological surveillance system during the 1990-1991 epidemic. Out of 2,521 confirmed cases of dengue, 34 cases of febrile acute illness with hemorrhagic manifestations were identified as possible cases of DHF/DSS, as well as two deaths associated to dengue. From these 36 cases, 12 cases were confirmed by laboratory exams as dengue with hemorrhagic manifestations. Examinations of clinical and laboratory data, and results of the autopsies suggested that the two deaths were cases of primary DHF/DSS. The difficulty of the health system in establishing the clinical suspicion of DHF/DSS was confirmed in the study. This resulted in delayed and inadequate clinical procedure. The present study also confirmed the need for a permanent active epidemiological surveillance system for the early identification of DHF/DSS suspect cases thus enabling quick and adequate control actions.

[Dengue in a urban locality of southeastern Brazil: epidemiological aspects]. / Dengue em localidade urbana da região sudeste do Brasil: aspectos epidemiológicos.

A dengue fever epidemic which occurred in Ribeirão Preto County, S. Paulo State, Brazil, during the period November, 1990 to March, 1991 has been analysed elsewhere. The general aspects of dengue epidemiology and control have been reviewed in this article. Emphasis is given to the analysis of some factors involved in the risk of dengue haemorrhagic fever and ecological aspects of the vector, as well as to the appropriateness of strategies for dengue eradication or control. Epidemiological characteristics of dengue, mainly those related to its occurrence in different geographical areas and periods of time are described. The Ribeirão Preto epidemic has thus, been set within the context of the spread of the disease at global level, in the Americas, and particularly in Brazil and S. Paulo State.

[Dengue epidemic in Ribeirão Preto, SP, Brazil: a preliminary note]. / Epidemia de dengue em Ribeirão Preto, SP, Brasil: nota prévia.

A preliminary note on an outbreak of dengue which occurred in the city of Ribeirão Preto, State of S. Paulo, Brazil, from November 1990 to March 1991, is given. One case of Level II Dengue Hemorrhagic Fever/Dengue Shock Syndrome (DHF/DSS) and two deaths associated with dengue related shock are described. Clinicians and epidemiologists are alerted to the possibility of sporadic DHF/DSS cases during outbreaks of classical dengue in formerly free areas.

[Measles in rural workers: a methodological essay in social epidemiology]. / Sarampo em trabalhadores rurais: ensaio metodológico de epidemiologia social.

The study of a measles epidemic in the Ribeirão Preto region, in 1984, showed a high proportion of cases occurring among people above 15 years of age. This finding led to the identification of a particular characteristic of the disease's distribution in the area, i.e. the high incidence among rural workers (especially those restricted to collective lodgings when working in agricultural and industrial activities related to sugar cane plantations). A methodological exercise of synthesis between the descriptive phase of the traditional epidemiology and the was carried out. This procedure aimed at incorporating some aspects of the social process of the area with a view to explaining this particular distribution of measles as a result to that social process (i.e. the pattern of the occurrence of measles among rural workers is understood as a historically determined social event). Finally, the need to consider the appearance of specific diseases in different human groups according to the social process into which they are inserted in disenssed in such a way that their history and specificity are taken into account.