A 68-year-old patient from Jiangsu province, who has since recovered, developed symptoms on Christmas Day and was admitted to hospital 
 
 A woman from eastern China has been confirmed as the first ever human case of H7N4 bird flu, according to Chinese authorities. 
 
 Officials in Hong Kong have advised citizens to avoid wet markets, live poultry markets or farms if travelling to the mainland over the week-long lunar new year holiday which starts on Thursday. 
 
 
 
 The 68-year-old patient from Jiangsu province, who has since recovered, developed symptoms on 25 December, was admitted to hospital for treatment on 1 January and was released on 22 January. 
 
 
 
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 “She had contact with live poultry before the onset of symptoms,” Hong Kong’s centre for health protection (CHP) said in an alert on Wednesday evening. “According to a report from the Chinese centre for disease control and prevention, upon analysis, the genes of the virus were determined to be of avian origin.” 
 
 A CHP spokesperson said the diagnosis had been confirmed earlier this week and added: “Travellers to the mainland or other affected areas must avoid visiting wet markets, live poultry markets or farms. They should be alert to the presence of backyard poultry when visiting relatives and friends. 
 
 “They should also avoid purchasing live or freshly slaughtered poultry, and avoid touching poultry/birds or their droppings. They should strictly observe personal and hand hygiene when visiting any place with live poultry. 
 
 “Travellers returning from affected areas should consult a doctor promptly if symptoms develop, and inform the doctor of their travel history for prompt diagnosis and treatment of potential diseases,” the CHP alert said. 
 
 
 
 According to the US government’s centers for disease control and prevention (CDC) the most frequently identified subtypes of avian influenza known to have infected human beings are the H5, H7 and H9 viruses although such transmissions are rare. There are nine known subtypes of H7 viruses, of which H7N4 is one and in most cases human infection is uncommon. 
 
 “The most frequently identified H7 viruses associated with human infection are Asian lineage avian influenza A(H7N9) viruses, which were first detected in China in 2013. While human infections are rare, these have commonly resulted in severe respiratory illness and death,” advice on the CDC website says. 
 
 “In addition to Asian lineage H7N9 viruses, H7N2, H7N3, H7N7 virus infections have been reported. These viruses have primarily caused mild to moderate illness in people, with symptoms that include conjunctivitis and/or upper respiratory tract symptoms.” 
 
 
 
 Authorities have been concerned about the possibility of a potentially devastating human bird flu pandemic in Hong Kong since late 1997 when 18 locals were infected with the H5N1 virus, six of whom died. 
 
 On Wednesday the CHP said it would “remain vigilant and work closely with the World Health Organization and relevant health authorities to monitor the latest developments”. It urged citizens “to maintain strict personal, food and environmental hygiene”. ||||| Mainland China has confirmed the world’s first human case of a virulent bird flu strain, prompting Hong Kong’s Centre for Health Protection to issue an alert for the city. 
 
 The centre said health authorities confirmed this month that a 68-year-old woman in Jiangsu province had been infected with H7N4 avian influenza after developing symptoms on December 25. 
 
 The woman was admitted to hospital on New Year’s Day and was discharged on January 22. 
 
 She had contact with live poultry before she developed symptoms but no person in close contact with the woman had similar symptoms, the centre said. 
 
 The authorities in mainland China did not say whether there was an outbreak of H7N4 in poultry. 
 
 The centre said the mainland health authorities confirmed “the genes of the virus were determined to be of avian origin”. 
 
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 The centre reminded Hongkongers heading to the mainland or other affected areas for the Lunar New Year to avoid visiting wet markets, live poultry markets or farms. 
 
 “They should be alert to the presence of backyard poultry when visiting relatives and friends. They should also avoid purchasing live or freshly slaughtered poultry, and avoid touching poultry/birds or their droppings,” a spokesman for the centre said. 
 
 “They should strictly observe personal and hand hygiene when visiting any place with live poultry.” 
 
 Anybody with symptoms should notify their doctor for prompt diagnosis and treatment, the spokesman said. 
 
 Health services have been on alert for a possible human bird flu pandemic after an outbreak of the H5N1 strain in Hong Kong in 1997 infected 18 people, killing six of them. The city culled millions of poultry and imposed strict controls on markets, farms and bird imports from the mainland to try to contain the virus’s spread. 
 
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 In November that year an outbreak of H7N4 occurred in chickens at two poultry farms in northern New South Wales in Australia but nobody was infected. 
 
 From 2011 to 2016, between 10 and 145 confirmed human cases of H5N1 were reported to the World Health Organisation annually. Last year, there were three cases in Egypt and one in Indonesia. 
 
 The WHO is also closely monitoring human bird flu cases of H7N9, with a total of 1,567 human cases reported globally, including 1,564 in the past five waves, mostly on the mainland. Hong Kong reported 21 cases of H7N9, all imported from the mainland. Taiwan had five, Canada two, Macau two and Malaysia one, also imported from the mainland. 
 
 The Hong Kong centre said another strain, H5N6, had sickened 19 people since 2014, with all of the cases occurring on the mainland. The latest case was reported on January 5 this year. ||||| BEIJING (Reuters) - China has reported the first human case of the H7N4 strain of bird flu in a woman in an eastern coastal province, though she has since recovered. 
 
 The winter is traditionally the high season for bird flu infections. 
 
 In a statement late on Wednesday, the Hong Kong government’s Centre for Health Protection said it had informed of the case by mainland China’s health ministry, the National Health and Family Planning Commission. 
 
 According to the commission, this was the first case of human infection with the H7N4 strain in the world, the Hong Kong government said. 
 
 The case involved a 68-year-old woman in Jiangsu province who developed symptoms on Dec. 25, was admitted to hospital on Jan. 1 and discharged on Jan. 22. 
 
 “She had contact with live poultry before the onset of symptoms. All her close contacts did not have any symptoms during the medical surveillance period,” the Hong Kong government said. 
 
 It cited the Chinese Centre for Disease Control and Prevention as saying the virus’ genes “were determined to be of avian origin”. 
 
 The H7N9 strain is far more common in China for humans. 
 
 Since 2013, at least 600 people have died in China and more than 1,500 people have fallen sick as a result of H7N9 bird flu virus. Some 40 percent of people hospitalized with the virus die. 
 
 China recorded just a single human case of H7N9 last month. Last year 192 people contracted the H7N9 strain, 79 of whom died. ||||| BEIJING—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. 
 
 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. 
 
 Uncertainty about the new bird-flu virus is raising concern among investors. Minggao Shen, Citigroup’s head of China research, talks about how H7N9 will affect the retail, airline and insurance sectors in China. 
 
 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. 
 
 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. 
 
 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. 
 
 Enlarge Image Close Reuters Shanghai technicians wearing protective suits began Friday to cull poultry at a wholesale market where the H7N9 bird-flu virus was detected. 
 
 Bird-Flu Toll Rises in China View Slideshow AFP/Getty Images A Chinese health worker inoculated a chicken at a farm in Shangsi, in southwest China's Guangxi province. 
 
 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. 
 
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 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. 
 
 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. 
 
 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. 
 
 "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. 
 
 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. 
 
 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. 
 
 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. 
 
 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, 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." 
 
 —James T. Areddy in Shanghai, Jeffrey Ng in Hong Kong and Aries Poon in Taipei contributed to this article. 
 
 Write to Josh Chin at josh.chin@wsj.com
– A year after the World Health Organization announced it was on "high alert" over outbreaks of bird flu, China has confirmed the first human case of strain H7N4. Health officials say a 68-year-old woman who fell ill in Jiangsu province on Dec. 25 was infected with the strain, though she recovered after being admitted to the hospital on Jan. 1 and was released Jan. 22, per the Guardian. Officials haven't said whether there's an outbreak of H7N4 affecting poultry, but they note the woman was in contact with live poultry before developing symptoms, reports the South China Morning Post. H7N4 is one of nine known subtypes of H7 viruses, but unlike H7N2, H7N3, H7N7, and H7N9, it has never before been seen in humans. Though still rare, H7N9 is among the most deadly strains for humans, having killed at least 600—about 40% of those hospitalized—since 2013, reports Reuters. Viruses H5 (with a mortality rate higher than 50%) and H9 (only one recorded death) have also been reported in humans, per the CDC. Alerted to the H7N4 case on Wednesday, Hong Kong's Center for Health Protection issued a travel alert ahead of a weeklong holiday for the Chinese Lunar Year, which begins Friday. Visitors to mainland China "must avoid visiting wet markets, live poultry markets, or farms," a rep says. "They should also avoid purchasing live or freshly slaughtered poultry, and avoid touching poultry/birds or their droppings."