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principles of epidemiologyin public health practice_part7

Địa điểm đánh giá của một dịch bởi nơi không chỉ cung cấp thông tin về mức độ địa lý của một vấn đề, nhưng cũng chứng minh hoặc các cụm mô hình có thể cung cấp manh mối quan trọng bệnh nguyên đó. | Place Assessment of an outbreak by place not only provides information on the geographic extent of a problem but may also demonstrate clusters or patterns that provide important etiologic clues. A spot map is a simple and useful technique for illustrating where cases live work or may have been exposed. Some spot maps indicate each patient s residence. If the map shows a cluster or other pattern such as cases along a road the investigator must consider possible explanations perhaps water supplies wind currents or proximity to a restaurant or grocery. A spot map like that used by John Snow in London in 1854 see Lesson 1 Figure 1.1 can give clues about mode of spread.31 For example clustering of cases in a wing of a nursing home is consistent with either a focal source or person-to-person spread whereas scattering of cases throughout the facility is more consistent with a widely disseminated vehicle or a source common to the residents that is not associated with room assignment such as a common dining hall or water supply. In an outbreak of pneumococcal pneumonia in a nursing home in New Jersey cases were more common in the north wing than in the south wing Figure 6.6 . Nursing home staff did report that the 2 residents of the south wing who developed pneumonia did spend much of their time in the north wing.32 Figure 6.6 Cases of Pneumonia by Room Nursing Home A New Jersey 2001 Adapted from Tan C. A preventable outbreak of pneumococcal pneumonia among unvaccinated nursing home residents in New Jersey during 2001. Infect Control Hosp Epidemiol 2003 24 848-52. This is trial versioiTve an aoeek www.adultpdf.com Often a spot map by site of presumed exposure is more informative than one by residence. Figure 6.7 shows the location of staff in two offices in the U.S. Senate s Hart Building who had nasal swabs positive for B. anthracis after an envelope containing anthrax spores was opened in their presence.33 To look for clustering in an outbreak of surgical wound infections