Concerns about a deadly new strain of bird flu intensified last week as the disease claimed a sixth life in eastern China and agricultural authorities in Shanghai ordered a wide-scale slaughter of poultry in an effort to stem its spread.
Avian-Flu：禽流感 intensify：增强，加剧 slaughter：屠杀，宰杀
The U.S. Centers for Disease Control and Prevention warned U.S. public-health departments and physicians to be on the lookout for signs of the new virus, a variant of the H7N9 strain of avian flu. The CDC said it is developing a diagnostic kit to send to U.S. states and China, and is working on a seed virus for a vaccine that could be prepared should the disease start spreading human-to-human.
variant：变体，不同的，多样的 diagnostic kit：诊断试剂盒 vaccine：疫苗
Flu experts said they are concerned about the new virus because it exhibits signs of being more readily able to infect humans from ailing birds than is another form of avian flu known as H5N1, which has been infecting people off and on for more than a decade.
exhibit：展示，显示 ailing：生病的，衰弱的
The number of people infected nationwide as of Sunday evening had risen to 21, according to the official Xinhua news agency, up from Friday's 16. The death toll was unchanged from Friday, Xinhua said. The latest was a 55-year-old male working in the live poultry trade in the Chinese province of Anhui who began exhibiting flu symptoms on March 28, Xinhua said.
poultry：家禽
The number of cases, while small, is large for the early stages of an outbreak, and some flu experts said the fact that they are spread over a relatively wide geographic region is reason for concern.
Among the people found to be infected, several are believed to have been in close contact with birds, including a 48-year-old who transported poultry, a 45-year-old poultry butcher and a 38-year-old chef.
Authorities stressed they have yet to find a case of human-to-human transmission, which would make the disease more dangerous; the cases they have seen appear to come from human contact with birds. 'So far there is no evidence that the H7N9 virus can be spread between human beings, which makes us relieved,' Wu Fan, director of the Shanghai Center for Disease Control and Prevention, said Friday.
Chinese authorities are investigating illnesses in the families of two of the people who had confirmed H7N9, to see if any members have the disease─a finding that could suggest human transmission.
Still, 'the fact that we haven't seen cases in contacts and haven't seen it widespread in children' and elsewhere 'are all reassuring,' said U.S. CDC Director Thomas Frieden. The U.S. agency has worked closely with Chinese public-health authorities to improve the country's flu surveillance and lab testing in recent years, and Dr. Frieden said he had a 'long conversation' Thursday night with his counterpart on the evolving situation.
reassuring：安心的，可靠的，安慰的 surveillance：监督，监视 counterpart：配对物，副本
No cases have been identified in the U.S. 'There are no specific steps people in this country need to take to protect themselves,' Dr. Frieden said.
Worries the new bird-flu strain in China will stifle air travel sent shares of the nation's airlines falling sharply Friday, triggering a broader selloff in airline and travel stocks world-wide. Hong Kong-listed shares of Chinese airlines, among the hardest-hit companies during the 2003 SARS outbreak, tumbled. Chinese flag carrier Air China Ltd. fell 9.8%, its biggest one-day decline since April 27, 2009. The benchmark Hang Seng Index was down 2.7% at 21,727. Shanghai-based China Eastern Airlines Corp. dropped 8.3%, its biggest single-day decline since October 2011.
stifle：使窒息，扼杀 selloff：清除存货 tumble：跌倒，下跌
Other governments in the region have made efforts to contain the disease. Hong Kong and Taiwan are stepping up temperature checks in airports, using sensors that screen passengers as they pass through a gate.
The world has become more than familiar over the past decade with avian flu, which typically circulates in birds and can jump to humans. The emergence and spread of H5N1 avian flu more than a decade ago prompted countries such as the U.S. to develop elaborate and expensive pandemic preparedness plans. H5N1 proved frighteningly deadly─killing 60% of those it infected─but despite infecting 622 people in 15 countries, it hasn't spread readily from one human to another.
pandemic：全国流行的，普遍的
Whether this new H7N9 flu, a different avian-flu strain, is deadlier than H5N1 isn't yet clear, because it isn't yet known how many people have been infected or how sick they are.
Still, the new H7N9 is more worrying than H5N1 in some ways. Genetic changes in the avian virus suggest it may be adapting to infect mammals, said Nancy Cox, a virologist who is the CDC's Atlanta-based flu chief.
mammal：哺乳动物 virologist：病毒学家
'The markers are there indicating the virus has moved toward more readily binding the type of receptors that are in the human airway,' she said. In addition, 'there have been a larger number of H7N9 cases in a relatively short period of time than we saw with H5N1,' Dr. Cox said.
But she cautioned that little is still known about the new virus. The CDC hopes to receive a virus isolate or isolates from China within the next week or so, she said, and will study the genetic changes further to try to determine how transmissible the virus may be among humans.
caution：警告
Another challenge is that unlike H5N1, which can kill birds, this H7N9 virus doesn't make birds very ill─so there is little sign it is spreading in flocks.
The appearance of the new virus has shaken China, where memories of the crippling 2003 outbreak of severe acute respiratory syndrome remain fresh. Unlike with SARS, the government has vowed to be transparent and release information as quickly as possible, though many in China remain skeptical.
respiratory syndrome：呼吸综合症 skeptical：怀疑的，不可知论的
China's state media and local governments have flooded social-media sites with information about H7N9, which scientists say may be susceptible to the two most powerful antiviral drugs, Tamiflu and Relenza.
susceptible：易受影响的，易受感染的
Shanghai authorities moved Friday to destroy thousands of birds, ordering the closure of wholesale poultry markets and instructing vendors in smaller markets to immediately cull their chicken populations. Authorities had banned sales of live pigeon and ducks starting the morning after discovering H7N9 in samples taken from pigeons at three wholesale markets.
wholesale：大规模的，批发 vendor：供应商，销售商 cull：挑选，屠宰
On Saturday the eastern city of Nanjing banned live poultry trade and closed markets, according to the official Xinhua news agency.
In Europe, shares in International Consolidated Airlines Group, IAG.MC -7.31% the parent company of British Airways and Iberia, was down 6.9% in London trading, leading declines across the sector and among FTSE 100 stocks.
Speaking at a Friday news conference in Shanghai, Shao Linchu, a deputy director at the Shanghai Agricultural Commission, said local authorities had slaughtered more than 20,000 birds at a market in the suburb of Songjiang on Thursday night, and were investigating the origin of infected pigeons discovered there.
The U.S. Consulate in Shanghai issued a statement Friday urging people to remain calm. 'At this point the risk for international disease spread is considered low,' the consulate said. 'The latest advisory from the World Health Organization as of April 4 is that no travel or trade restrictions with China should be applied based on the current information.'