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zoom RSS 成人の百日咳患者が、重症化しやすい乳幼児への感染源に/百日ぜき ワクチン

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 米国や豪州では成人の百日咳患者が多数存在し、重症化しやすい乳幼児への感染源となっている。米国では年間60万人の成人患者発生が推定されている。咳が2−4ヶ月続き、肺炎・肋骨骨折・失神をきたし、休職通院に追われてしまう。米国では2005年から、成人への三種混合ワクチンTdap(百日ぜき・ジフテリア・破傷風)が使用可能となった。10年ごとの接種が推奨されている。

 確定診断のためには、鼻咽頭からの百日咳菌の分離同定が必要である。培養には、特殊培地を要する。菌はカタル期後半に検出され、痙咳期に入ると検出されにくくなるため、実際には菌の分離同定は困難なことが多い
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百日咳
http://idsc.nih.go.jp/idwr/kansen/k03/k03_36.html
(国立感染症研究所感染症情報センター)
 百日咳(pertussis, whooping cough )は、特有のけいれん性の咳発作(痙咳発作)を特徴とする急性気道感染症である。母親からの免疫(経胎盤移行抗体)が期待できないため、乳児期早期から罹患し、1歳以下の乳児、ことに生後6 カ月以下では死に至る危険性も高い。
 臨床経過は3期に分けられる。
1)カタル期(約2週間持続):通常7〜10日間程度の潜伏期を経て、普通のかぜ症状で始まり、次第に咳の回数が増えて程度も激しくなる。
2)痙咳期(約2〜3週間持続):次第に特徴ある発作性けいれん性の咳(痙咳)となる。これは短い咳が連続的に起こり(スタッカート)、続いて、息を吸う時に笛の音のようなヒューという音が出る(笛声:whoop)。この様な咳嗽発作がくり返すことをレプリーゼと呼ぶ。しばしば嘔吐を伴う。発熱はないか、あっても微熱程度である。1992〜1994年の米国での調査によると、致命率は全年齢児で0.2%、6カ月未満児で0.6%とされている。
3)回復期(2, 3 週〜):激しい発作は次第に減衰し、2〜3週間で認められなくなるが、その後も時折忘れた頃に発作性の咳が出る。全経過約2〜3カ月で回復する。
 成人の百日咳では咳が長期にわたって持続するが、典型的な発作性の咳嗽を示すことはなく、やがて回復に向かう。軽症で診断が見のがされやすいが、菌の排出があるため、ワクチン未接種の新生児・乳児に対する感染源として注意が必要である。
 確定診断のためには、鼻咽頭からの百日咳菌の分離同定が必要である。培養には、ボルデ・ジャング(Bordet ‐Gengou)培地やCSM (cyclodextrin solid medium )などの特殊培地を要する。菌はカタル期後半に検出され、痙咳期に入ると検出されにくくなるため、実際には菌の分離同定は困難なことが多い。血清診断では百日咳菌凝集素価の測定、ペア血清(2 週間以上の間隔)で4 倍以上の抗体価上昇があるか、シングル血清で40 倍以上であれば診断価値は高い。また最近では、ELISA 法による抗PT 抗体、抗FHA 抗体の測定も時に行われる。研究室レベルでは菌の染色体DNA 解析、PCR 法などによる病原体遺伝子の検出も行われる。

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香川大・百日ぜき、異例の成人集団感染
http://www.asahi.com/health/news/OSK200706050074.html
2007年06月06日
 香川大学で、しつこいせきなどの症状を訴える学生や職員が相次ぎ、休講などの対応を取った問題で5日、学生らからとった検体から百日ぜき菌の遺伝子が見つかり、日本で例のない成人百日ぜきの大規模集団感染だったことが分かった。検体を調べた国立感染症研究所は「地域に、気づかないまま感染が広がっている可能性がある」といい、重症化しやすい乳児は、できるだけ早い機会に予防接種を受けるよう呼びかけている。
 香川大では4月以降、しつこいせきなど、百日ぜきに似た症状を起こす学生や職員が続発。同大によると、4日までに計216人が症状を訴えた。百日ぜきかどうか調べるため、5月28日以降に症状を訴えてきた学生19人分ののどの粘液を感染研に送って検査を依頼。12人分から百日ぜき菌の遺伝子が見つかった。
 感染研細菌2部の荒川宜親部長は「香川大の流行が本当に百日ぜきか、半信半疑だったので、菌が高率に見つかって、実は驚いた。成人の百日ぜき集団感染は、聞いたことがない。なぜ香川大で起きたのか謎だ」と話す。
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A "new age" in pertussis prevention new opportunities through adult vaccination.
Cortese MM, Baughman AL, Brown K, Srivastava P.
Am J Prev Med. 2007 Mar;32(3):177-185.

National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia 30333, USA. mcortese@cdc.gov

BACKGROUND: For the first time, pertussis vaccines for adolescents and adults (combined with tetanus and diphtheria toxoids [Tdap]) became available in the United States in 2005. Despite a fully implemented U.S. childhood pertussis vaccination program, substantial morbidity because of pertussis continues to occur. To reduce this morbidity, the Advisory Committee on Immunization Practices recommended Tdap for all adolescents and adults in place of the next tetanus-diphtheria booster. As background for the basis of these recommendations, we summarize data on the morbidity and incidence of pertussis in U.S. adults and the role of adults in transmitting pertussis to young infants. METHODS: A MEDLINE search was performed in March 2006 for data on pertussis incidence rates and cough illness because of pertussis among U.S. adults (prospective, nonoutbreak studies were selected) and pertussis complications in adults. Data from the national passive surveillance system were also analyzed in October 2005. RESULTS: The true adult burden is estimated at more than 600,000 cases annually in the United States. Adults with pertussis commonly cough for 2-4 months, often resulting in repeated medical visits and missed work. Complications include pneumonia, rib fractures, and cough syncope. Adults are an important source of pertussis for young infants, who have the highest risk of hospitalization and death. CONCLUSIONS: The morbidity from pertussis in adults can be substantial, the incidence of pertussis in U.S. adults is high, and adults transmit infection to young infants. Providers now have the opportunity to reduce the burden of pertussis by vaccinating adults with Tdap.
PMID: 17296469 [PubMed - indexed for MEDLINE]

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Pertussis in Australia today - a disease of adolescents and adults that can kill infants.
Senanayake S.
The Canberra Hospital, The Australian National University Medical School, Australia. sanjaya.senanayake@act.gov.au
Aust Fam Physician. 2007 Jan-Feb;36(1-2):51-6.

BACKGROUND: Adolescents and adults are the main reservoir of pertussis infection in Australia today. Diagnosis in these age groups can be difficult because of atypical clinical presentations and limitations of laboratory investigations. OBJECTIVE: This article discusses the common presentation of pertussis in adults and adolescents, the use and limitations of laboratory testing, and appropriate treatment and prophylaxis. DISCUSSION: The reason for treating cases and providing chemoprophylaxis for contacts is to prevent infection in infants, who account for 90% of deaths from pertussis. Treatment with the newer macrolides appears to be as effective as erythromycin and with less side effects; however, roxithromycin should not be used as its in vivo efficacy is unproven. The majority of pertussis cases will be seen in general practice - most likely during the infectious period - therefore general practitioners need to consider being vaccinated with dTpa against pertussis.
PMID: 17252087 [PubMed - indexed for MEDLINE]

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Acellular Pertussis Vaccine Proves Effective in Adults, Adolescents
http://www3.niaid.nih.gov/news/newsreleases/2005/pertussis.htm
A vaccine to protect adults and adolescents against illness due to Bordetella pertussis infection―or whooping cough―has proved more than 90 percent effective in a national, large-scale clinical study, according to research results published in this week’s issue of The New England Journal of Medicine. The vaccine, researchers say, could be used to stem the increase in pertussis cases among adults and adolescents in the United States and thereby prevent the prolonged cough illness, which can result in hospitalization, pneumonia and cracked ribs in those populations. An important additional benefit of the vaccine may be to decrease transmission of the B. pertussis bacterium to infants, who are particularly vulnerable to severe illness, complications and death resulting from whooping cough. The illness annually affects 50 million people worldwide.
“During the 1990s, the number of reported pertussis cases among adolescents and adults more than doubled in the United States as the protective effects of earlier childhood immunizations have waned,” says Anthony S. Fauci, M.D., director of the National Institute of Allergy and Infectious Diseases (NIAID), National Institutes of Health, which funded the study. “This new study shows that an effective adult acellular pertussis vaccine is feasible and if routinely used could provide the U.S. population greater protection against the disease.”
Known as the Adult Pertussis Trial, the 2.5-year study involved 2,781 healthy individuals between 15 and 65 years of age. Volunteers were randomly assigned to one of two similarly sized groups that received either the acellular pertussis vaccine or the control hepatitis A vaccine (Havrix). For purposes of the trial, pertussis cases were defined as illnesses with a cough lasting at least five days that occurred more than 28 days after vaccination and were confirmed through blood and nasal mucus testing.
Joel I. Ward, M.D., of the Center for Vaccine Research at the University of California, Los Angeles, led the multicenter clinical study. GlaxoSmithKline, based in Philadelphia, supplied both the pertussis test vaccine and the hepatitis A vaccine.
Ten confirmed cases of pertussis occurred during the trial―nine cases were among the individuals who received the hepatitis A vaccine. The researchers concluded that a single dose of the test vaccine was safe and 92 percent effective in protecting adolescents and adults against pertussis.
Although infants are routinely inoculated against pertussis through a series of three diphtheria-tetanus-acellular pertussis (DTaP) vaccines given in the first year of life, immunity has been shown to weaken after six to 10 years.
“The purpose of an adult pertussis vaccine is to prevent the disease in adults with the added benefit that it may help to put up a roadblock in the transmission of the disease, so that parents, grandparents and other adults are not unknowingly passing the disease along,” says David Klein, Ph.D., of NIAID’s Respiratory Diseases Branch.
In 2004, the highest number of U.S. pertussis cases was among individuals 10 to 18 years of age with roughly 6,500 cases reported, according to data from the Centers for Disease Control and Prevention. Infants less than six months old experienced the second highest number of pertussis cases last year, with an estimated 2,200 cases reported.
NIAID is a component of the National Institutes of Health, an agency of the U.S. Department of Health and Human Services. NIAID supports basic and applied research to prevent, diagnose and treat infectious diseases such as HIV/AIDS and other sexually transmitted infections, influenza, tuberculosis, malaria and illness from potential agents of bioterrorism. NIAID also supports research on transplantation and immune-related illnesses, including autoimmune disorders, asthma and allergies.

Reference: JI Ward et al. Efficacy of an acellular pertussis vaccine among adolescents and adults. The New England Journal of Medicine 353(15):1555-1563 (2005).

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百日ぜきの患者数増加/大人の割合増加 /百日ぜき ワクチン
6月始めに香川大での集団感染があり、 06/06 ブログで紹介した。 成人の百日咳患者が、重症化しやすい乳幼児への感染源に/百日ぜき ワクチン http://kurie.at.webry.info/200706/article_21.html ...続きを見る
医師の一分
2007/08/03 22:05

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成人の百日咳患者が、重症化しやすい乳幼児への感染源に/百日ぜき ワクチン 医師の一分/BIGLOBEウェブリブログ
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