【正文】 ecessary to identify sources of contamination and quickly limit a public health threat by removing these sources. ? Ascertain the distribution and production chain for a food product to facilitate effective recall. ? Clarify the point or points at which the implicated food was likely to have bee contaminated Traceback Results Follow up ? The implicated seed lot was a blend of 5 lots from fields of four farmers and was harvested between 1994 and 1996. The seed processor and the farmers were located in Idaho. ? Inspection of the alfalfa fields revealed three possible sources of contamination: cattle manure, irrigation water, and deer feces. ? Manure is not normally applied to alfalfa fields in Idaho ? Cattle feed lots were mon in this area and the alfalfa fields of one farmer were adjacent to a feed lot. ? Manure may have leaked or been illegally dumped onto the alfalfa fields or runoff water from neighboring fields, contaminated by manure, may have been used to irrigate the alfalfa fields. ? In addition, three of four farmers occasionally saw deer in their fields and one field was situated next to a wildlife refuge. Steps in Outbreak Investigation ? Verify the diagnosis ? Confirm the outbreak ? Case definition ? Descriptive epidemiology ? Develop a hypothesis ? Test the hypothesis ? Refine hypothesis / Execute additional studies Steps in Outbreak Investigation ? Verify the diagnosis ? Confirm the outbreak ? Case definition ? Descriptive epidemiology ? Develop a hypothesis ? Test the hypothesis ? Refine hypothesis / Execute additional studies ? Implement control and prevention measures What interventions are Needed? ? 2 issues: ? 1) the immediate problem with this implicated lot of seed ? 2) the larger issue of seed sprouts as vehicles for pathogenic What interventions are Needed? ? Implicated seed lot ? all remaining seeds and alfalfa sprouts from the implicated lot should be removed from the market. ? Persons who have purchased sprouts from the implicated lot should be instructed to destroy any remaining sprouts or return them to the store at which they were purchased. ? The producers of these particular seeds should be informed of the need to protect alfalfa and other seeds used in sprouting from contamination during growing, harvesting, and packing. ? Specific sources of contamination should be identified and eliminated from these growing sites. What interventions are Needed? ? Seed sprouts are high risk vehicle for foodborne diseases ? Continue applied research to find ways to successfully decontaminate the seeds/sprouts. ? Educate sprout growers on appropriate growing conditions and handling of sprouts to limit contamination. ? Educate the public about the riskiness of sprouts ? Persons at high risk for plications of infection (., children 5 years of age, immunopromised individuals, and the elderly) avoid sprouts. ? Require sprout producers to label sprouts as risky foods ? Remove sprouts from the market for human consumption until their safety can be assured. Steps in Outbreak Investigation ? Verify the diagnosis ? Confirm the outbreak ? Case definition ? Descriptive epidemiology ? Develop a hypothesis ? Test the hypothesis ? Refine hypothesis / Execute additional studies ? Implement control and prevention measures Steps in Outbreak Investigation ? Verify the diagnosis ? Confirm the outbreak ? Case definition ? Descriptive epidemiology ? Develop a hypothesis ? Test the hypothesis ? Refine hypothesis / Execute additional studies ? Implement control and prevention measures ? Communicate findings Communicate Findings ? The implicated seed lot was not distributed to any other sprouting panies. The remaining 6,000 lbs. of seed was immediately removed from the marketplace. ? The Idaho Division of Food and Drugs held meetings at which public health officials explained to seed growers the need to protect alfalfa and other seeds used in sprouting from contamination during growing, harvesting, and packing. ? Public television and radio announcements about the risk of cont。病例分布在資陽、內(nèi)江、成都等 12 個市， 37 個縣（市、區(qū)） , 131 個鄉(xiāng)鎮(zhèn)（街道） , 195 個村（居委會）。同上。其中疫情最嚴重的資陽、內(nèi)江溫度較去年同期高近 2 ℃ ，濕度高約 2 ～ 5 個百分點。與病死豬密切接觸的人群可能是該病的高危人群，尤其有傷口或皮膚破損者更易感。衛(wèi)生條件相對較好的養(yǎng)殖大戶和規(guī)?；B(yǎng)殖場未見疫情報告。 休克等癥狀。 x 回憶： 平均潛伏期（ X）＝ (M2－ M0 )(M0－ M1 ) / [ (M2－ M0 )－ (M0－ M1 )] M1：病例數(shù)所占總數(shù)比例 16％時點； M0： 50％時點； M2： 84％時點、 暴露日期＝ M0－ X ? 根據(jù)初步調(diào)查結(jié)果，形成假說，然后進行病例對照、隊列研究和流行病學(xué)實驗研究等，最后闡明爆發(fā)原因及流行特點和規(guī)律，以采取有效防治措施。 3. 初步調(diào)查。 ? 點源流行后繼發(fā)蔓延流行，其流行曲線表現(xiàn)為陡峭的單峰曲線（點源流行）右側(cè)拖一長尾（蔓延流行）。 如圖 132， 設(shè) m1為累計發(fā)生16%病例數(shù)的時間 ， m0為 累計發(fā)生 50%病例數(shù)的時間 ，m2為累計發(fā)生 84%病例數(shù)的時間 。 流行中受染者一般不再傳播給其他易感者 。潛伏期變異較大時，則“代”的區(qū)分不明顯。③經(jīng)驗豐富的公共衛(wèi)生醫(yī)師進行快速的現(xiàn)場訪問，根據(jù)臨床特征，結(jié)合實驗室證據(jù)判斷爆發(fā)信息的確鑿性。） ? 確定流行類型（一次同源性暴露，病例常集中在一個最短、最長潛伏期；多次暴露，同源多次暴露的發(fā)病曲線具有兩個以上高峰，而連續(xù)性暴露則發(fā)病曲線具有兩個以上高峰或者持續(xù)高峰）。 7 月 16 日起，發(fā)病明顯增多， 22 日達到高峰， 19 ～ 25 日發(fā)病穩(wěn)定在較高的水平， 7 月 28 日開始下降，累計發(fā)生病例 204 例，死亡 38 例。 （二）三間分布 1 ．空間分布特征 ( 1 ）發(fā)病區(qū)域相對集中，主要發(fā)生在四川資陽、內(nèi)江等地。臨床上起病急，多為突起高熱，肢體遠端部位出現(xiàn)癖點、癖斑，早期多伴有胃腸道癥狀、休克，病情進展快，很快轉(zhuǎn)人多器官衰竭，如呼吸窘迫綜合征，心力衰竭，彌散性血管內(nèi)凝血和急性腎衰等，預(yù)后較差，病死率極高。通過現(xiàn)場流行病學(xué)調(diào)查，同時還發(fā)現(xiàn)腦膜炎癥狀為主的病例，主要臨床表現(xiàn)為頭痛、高熱、腦膜刺激征陽性等。 3 ．臨床病例診斷標準參考美國 CDC 1993 年制訂的鏈球菌中毒性休克綜合征診斷標準，并結(jié)合本起疾病的特點修正制訂診斷標準為： ( 1 ）鏈球菌中毒性休克綜合征； ① 檢出鏈球菌：從無菌部位如血液、腦脊液等處分離到鏈球菌。對病人的密切接觸者予以 7 天的醫(yī)學(xué)觀察。 inhibits recognition of extension of outbreak into other states. ? Dates reasonable? ? Need more information ? Could limit the number of secondary cases included in the study that could interfere with identification of the initial source of the outbreak. Steps in Outbreak Investigation ? Verify the diagnosis ? Confirm the outbreak ? Case definition Steps in Outbreak Investigation ? Verify the diagnosis ?