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zoom RSS 百日ぜき流行の再来/米国医療事情

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 気分は悪くなく、熱もないが、咳き込みが何週間も続く。喘息の薬は効果無し。
 百日ぜきはずっと前に根絶されたと思われていたが、最近10代や成人での発病が増加している。
 百日ぜきは乳幼児の主要な死因の一つであったため、1940年代にワクチンが米国で最初に導入された。
 DTaPとして知られているワクチンはジフテリアと破傷風とともに百日咳からの保護をする。2,4,6ヶ月での3回の接種と、15-18ヶ月の4回目、入学前の5回目の接種をする。40年前より多くの病気が予防接種で激減したが、百日ぜきは決して完全に消えなかった。5回の予防接種でも終生の免疫は得られないことが次第に判明し、2005年からは、Tdapというブースターワクチンによる5-10年ごとの追加接種が成人に推奨されるようになった。
 11-64才の人にTdapブースターが2005年にFDA食品医薬品局により承認されたが、CDCによれば、接種率は約30%であるという。
 病気の初期1-2週間は鼻水、くしゃみ、眼球結膜の充血、軽い咳、微熱がでる。風邪に似ており、この時期は伝染しやすい。第2ステージに咳が悪化する。乳児では咳き込んだ後に長い吸気が叫び声のように聞こえるので、whooping coughという名前の由来になっている。子どもではしばしば"whoop"するが、大人ではみられない。激しく咳き込み、その後嘔吐する。乳児では呼吸困難となる。
 メイヨ・クリニックのRobert Jacobsonによれば、乳幼児では入院治療が必要であるという。成人から感染するのが一般的であるという。成人で診断が見過ごされ、年に約60万人が感染すると概算している。
 CDCの統計では2004-2005年で25,000、2006年は10,000例が報告された。
 早期に診断されれば抗生物質での治療が一般的であり、家族内感染を防ぐため予防投与が行われる。診断が遅れた場合は、抗生物質の効果は明瞭でない。
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間違いだった百日ぜきの流行/検査による擬陽性 米国
http://kurie.at.webry.info/200708/article_45.html
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
原因不明の長引くせき、大人も百日ぜき注意
http://kurie.at.webry.info/200706/article_39.html
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
http://kurie.at.webry.info/200708/article_5.html
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Extreme Coughing: Whooping Cough Makes a Comeback
More cases in teens and adults; parents often unaware of new booster vaccine
By CARI NIERENBERG
ABC News Medical Unit
Dec. 26, 2008
http://abcnews.go.com/Health/ColdandFluNews/story?id=6512732&page=1

A young woman in her early 30s was the picture of health: She was fit and ran regularly but had this nagging cough that she couldn't seem to shake.

画像Cough
Most parents are not aware that whooping cough remains a formidable health threat for young children.
(Corbis Images)

Because she didn't feel sick and had no fever, she figured it was a cold. Yet the coughing continued for weeks. So she went to her doctor, who suspected it was asthma because the hacking seemed to increase after she'd finished running. But asthma medications brought her no relief.

Frustrated that she couldn't run, the woman sought a second opinion from the Mayo Clinic in Rochester, Minn.

She learned the unexplained cough wasn't asthma. And it wasn't bronchitis or pneumonia either.

It was whooping cough.

In recent years, whooping cough has been diagnosed increasingly in teens and adults, although the disease typically had its most serious complications in infants.

Wasn't Whooping Cough Eliminated Long Ago?

Whooping cough is an illness caused by the bordetella pertussis bacteria. Health professionals tend to call this extremely contagious infection pertussis.

Reported cases of whooping cough have tripled in the United States since 2001, according to the Centers for Disease Control and Prevention, seen mainly in adolescents and adults, said Tami Skoff, a pertussis epidemiologist in the division of bacterial diseases at the CDC in Atlanta.

"But the jury is still out on whether it's a real increase in disease or an increase in reported disease due to improved diagnostic testing and more awareness among health professionals," she said.

Skoff suggested that there appears to be a shift in the epidemiology of the disease from infants to adolescents and adults. "From the data it looks like what's occurring is waning immunity."

Vaccine Causes Decline

A pertussis vaccine was first introduced in the United States in the 1940s, because whooping cough had been one of the most common diseases and a major cause of death in childhood.

The vaccine, known as DTaP, provides protection against pertussis along with diphtheria and tetanus. It's typically given as three shots at roughly 2, 4 and 6 months of age; a fourth shot is given between ages 15 and 18 months, and a fifth between ages 4 and 6, before children start school.

Although vaccination caused a sharp decline in the disease for more than 40 years, whooping cough never fully disappeared.

Whooping Cough Booster Vaccine Introduced in 2005

As more cases were reported, it became clear that the five-shot series was not providing lifelong protection. Immunity seemed to wear off five to 10 years after the last shot was received, making teens and adults vulnerable to infection once again.

In 2005, a new booster vaccine known as Tdap was approved by the FDA. This one-time booster dose is given to people between the ages of 11 and 64, assuming they have completed the childhood series.

But word of Tdap has not yet reached all parents of school-age children. While coverage rates for the childhood pertussis vaccine series hover around 90 percent of recommended recipients, rates for the Tdap booster are now around 30 percent, according to the CDC.

"It's still new," Skoff said. "With education campaigns, we expect this number to go up."

A growing awareness of the booster vaccine, which some middle schools require for entrance, could help stem the tide. In the meantime, both parents and patients still seem surprised when they find out they have whooping cough.

"I didn't think that disease existed anymore," is the response Dr. Judith Guzman-Cottrill, an assistant professor of pediatric infectious disease at Oregon Health and Science University in Portland, often gets when she tells a parent that their child has been diagnosed with pertussis.

And when she tells teenagers they have whooping cough, the typical reaction is "I thought that was a baby disease."

A Terrible Disease in Infants

The first stage of the illness typically starts out with a watery, runny nose, sneezing, redness of the eyes, a mild cough, and a low fever for the first week or two. To doctors and parents, it looks very much like the common cold.

The tricky thing about pertussis is that although it resembles a cold in this early stage, this is also when it's most contagious, pointed out Guzman-Cottrill.

But during the second stage, the cough worsens. An infant gets intense coughing fits and brings up thick phlegm. At the end of a severe coughing spell, the baby will try to catch its breath to recover and often takes a long inhalation, which sounds like a whoop. That's where the name whooping cough comes from.

Babies often "whoop," but teens and adults might not. And more than half of patients cough so severely that they vomit afterward.

"The forcefulness of the cough is really dramatic sometimes to the point of rib fracture," said Guzman-Cottrill. Or worse still. Some babies have such severe breathing difficulties that their tiny lungs and heart give out.

Infants With Whooping Cough Hospitalized

When they have whooping cough, infants are most always hospitalized, explained Robert Jacobson, chairman of the department of pediatric and adolescent medicine at the Mayo Clinic. "They look terrible." And infants with pertussis typically get it from adults, he noted.

Compared to younger children, teens and adults don't usually get the classic case of whooping cough and they might not look ill, Jacobson noted. He said they're likely to have an annoying cough that lasts for weeks and weeks.

"That's why it's sometimes called 'the 100-day cough,' which is a great name for it," he said.

Jacobson believes that pertussis is greatly underdiagnosed, and he said his best estimate is that there are about 600,000 cases of it in American adults a year.

Statistics from the CDC, however, paint a very different picture. The CDC reports 10,000 total U.S. cases in 2007, 15,000 cases in 2006 and 25,000 in both 2005 and 2004.

Jacobson also explained that the pertussis bacteria can live in dried mucus for three days, so whooping cough can be a real problem in adults who are undiagnosed and untreated. Adults could potentially pass it on to infants if they are exposed to them in their first few highly contagious weeks of illness, when the respiratory droplets from a cough can propel germs into the air.

According to Jacobson, antibiotics are the typical treatment if the disease is caught early. Antibiotics are also given to family members to reduce the possibility of spreading. He said it's less clear whether antibiotics help with patient symptoms when the disease is diagnosed late.

Making 'Whoopies' to Prevent Whooping Cough

When two twin girls in Phoenix were stuck at home with whooping cough this summer, they turned what could have been an unpleasant experience into a positive one.

The 11-year-olds, Ileyna and Flori, caught whooping cough in July while away at summer camp. They came home with very bad coughs, which at first were thought to be bronchitis but were later determined to be pertussis after an astute health professional decided to run one more test.

"It was a fluke that we found out what it was," said the twins' mother, Julie Witenstein.

"When I had to share the news with all the parents of the children the girls were exposed to, I realized that few of them knew about the pertussis booster vaccine."

The girls had had all their childhood vaccines but had just turned 11 and had not yet had the booster. While they were convalescing at home, a notice arrived from the middle school the girls would attend in August, explaining that the Tdap booster was required before enrolling.

The notice would arrive too late for the twins, but while indoors they kept themselves busy with a crafts kit a friend had given them. They started to decorate bottle caps with glitter, beads, buttons and glue.

The decorated bottle caps first started out as refrigerator magnets. But as the girls continued working on the caps, their creativity took hold and they put pins or tacks on the backs, or hooks to make necklaces or holiday ornaments. They made hundreds of decorated bottle caps and eventually started a business.

And that's how Whoopies was born, explained Witenstein.

Ileyna and Flori have been selling Whoopies at their parents' gymnastics studio and at a neighborhood art fair. With each sale they share their story about whooping cough, hand out a reminder on the importance of preteen vaccination, and give a portion of the proceeds to the Arizona Partnership for Immunization, a public health organization in the state that soon hopes to have a Web site to take orders for Whoopies.

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Cold & Flu season is here! Visit the ABCNews.com OnCall+ Cold & Flu Center to get all your questions answered about these nasty viruses.

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