消除猪流感在美国中西部相当多儿童中的流行,但是收效甚微.doc

A Swine Flu Virus Takes Off in Children at Midwestern Fairs But Makes Little HeadwayHands-off learning. CDC recommends that children wash their hands after being near pigs.Credit: Muffet/Liz WestAn unusual influenza virus has caught the attention of public health officials because it has rapidly spread from pigs at U.S. county fairs to children. The virus, a variant of an H3N2 strain that seasonally infects humans, has not caused severe disease. Scant evidence exists that it can spread between people, and the vast majority of cases are in two states.Epidemiologist Joseph Bresee of the U.S. Centers for Disease Control and Prevention (CDC) in Atlanta explained in a teleconference today that 145 cases have been confirmed since 12 July, a big jump from last week when CDC tallied only 16 confirmed cases since that date. “This is clearly a significant increase since last weeks total, ” he said, adding that this reflects increased testing and the large number of county fairs now taking place.Bresee said that more than 90% of the cases occurred in children, most of whom had direct or indirect contact with pigs, and all but two were in Indiana and Ohio. “At this point, theres no evidence of sustained, efficient, human-to-human spread in the community, ” he said. “Our seasonal influenza systems are active and have not shown any signs in an increase in influenza activity. This is not a pandemic situation. But of course CDC is continuing to monitor the situation closely.”H3N2v first surfaced in July 2011 and infected 12 additional people before disappearing this past winter. Researchers were intrigued because the virus has an internal “M” gene that matches one found in the pandemic H1N1 virus that rapidly infected humans throughout the world in 2009 and 2010. CDC virologist Michael Shaw says he suspects the M gene, which affects how well the virus grows in its host, plays a role in the current transmissions. “Theres something about that gene that gives it an advantage for circulating in pigs, ” Shaw says. “And if it becomes more common in pigs, it gives more of a chance to jump into humans.” But Shaw says theres no evidence that this M gene by itself leads to human-to-human transmission.Excluding this outbreak and the pandemic H1N1 virus, CDC has recorded only 35 total cases of influenza viruses stemming from pig-to-human transmission in the United States during the past 7 years.Bresee said that two people were hospitalized because of H3N2v infections but were released. He urged people who visit animals at county fairs to wash their hands frequently and to not eat or drink around pigs. Studies have shown that the current flu vaccine, which contains an H3N2 component, likely will not protect against this strain, but adults presumably have immunity from exposure to “wild type” strains of influenza and previous vaccines that provide some protection against the new variant.CDC plans to release an update about the outbreak tomorrow in its issue of the Morbidity and Mortality Weekly Report.一个不寻常的流感病毒，引起了公共卫生官员的注意，因为它在美国的一些县城农畜品交易会上，已迅速地由猪向儿童传播。该病毒是H3N2毒株的一个变种，其毒力不引起严重的病情。很少有证据表示它能在人之间传播，现极大多数的病例集中在2个州。在亚特兰大的美国疾病控制和预防中心（CDC）的流行病学家约瑟夫布莱希（Joseph Bresee），于今天（8月9日）的电视电话会议上宣布，自7月12日CDC确诊合计仅16个病例以来，这个数据从上周起，大幅度地上升至145例。他说：“这是很清楚的，自上周起感染的总人数显著地增加。”这个数据的增加，反映了检测的增加和现在大量的县城农畜产品交易会正在举行。布莱希说，超过90%以上的病例发生在儿童，在印第安那州和俄亥俄州，他们当中除2 例以外，极大多数直接或间接地接触过猪。他说：“根据这一情况，在人群中缺乏持续和有效率的人传人证据。”“我们的季节性流感防治系统是充满活力的，并没有任何迹象显示流感活动的增加。这不是一个大流行的态势。但当然，CDC将继续密切地监测这一疫情。H3N2v（译注v代表变种）首次出现于2011年7月，在去年冬天消失之前，感染人数只增加到12个。这一病毒吸引了研究人员的注意，因为该病毒内的“M”基因，与引起2009年和2010年世界各地迅速感染人类的大流行中发现的H1N1的“M”基因相符合。CDC的病毒学家迈克尔肖（Michael Shaw）说，他觉得这个M基因影响病毒在宿主中如何更好地生长，于流行传播中起着作用。肖说：“关于这个基因在猪中传播具有一种优势的情况，如果它在猪中变得更为常见，这就使它更加具备了传播给人类的机会。”但是，肖说，没有证据表明会由这个M基因本身引起人到人的传播。扣除这次爆发和H1N1大流行的感染人数，在过去7年中，美国仅记录总数35例由猪传人的流感病毒。布莱希说，2个因H3N2v感染的住院病例已经出院。他呼吁在县城农畜产品交易会上观看动物的人，希望他们经常地冼手，并不可在猪的周围饮食。研究表明，现在的流感疫苗，其中包含了H3N2的组分，可能儿童们会对这一变异株不具有免疫力，但成年人很可能由于接触过流感病毒的“野型”株以及先前的疫苗，而具有对这一新变种的一些免疫力。CDC计划在明天（8月10日）发布疫情的发病率和死亡率周报，提供关于这次疫情的最新情况。infection infeknn. 感染；传染；影响；传染病seasonal si:znladj. 季节的；周期性的；依照季节的virus vairsn. 病毒 病毒；恶毒；毒害vaccine vksi:nn. 疫苗；牛痘苗; adj. 疫苗的；牛痘的sustain ssteinvt. 维