H7N9 Bird Flu Outbreak

BBC News

Taiwan reports first bird flu case outside China

April 24, 2013

A 53-year-old businessman in Taiwan has the first case of the H7N9 bird flu virus outside mainland China, health officials there have confirmed. The man is in a serious condition in hospital days after returning from the Chinese city of Suzhou, officials say. China has confirmed 108 cases of H7N9 since it was initially reported in March, with at least 22 people dead. The World Health Organization (WHO) says this strain appears to spread more easily from birds to humans. The man in Taiwan was brought to hospital three days after he arrived from Suzhou via Shanghai, officials say.

He was not in contact with poultry, nor had he eaten undercooked birds while in Suzhou, Taiwanese Health Minister Chiu Wen-ta told local media. Taiwan’s President Ma Ying-jeou has ordered the health department to step up prevention measures, says the country’s Central News Agency. Experts are still trying to understand the H7N9 virus, and it has not yet been determined whether it could be transferred between humans. “This is definitely one of the most lethal influenza viruses we have seen so far,” WHO flu expert Dr Keiji Fukuda said at a news conference in Beijing. “When we look at influenza viruses this is an unusually dangerous virus.”

He added that the WHO team was just beginning its investigation. But he said that based on the evidence, “this virus is more easily transmissible from poultry to humans than H5N1”, a strain which spread in 2003. Dr Fukuda led a team from the WHO on a one-week China visit to study H7N9, along with Chinese officials from Beijing and Shanghai. The WHO believes that poultry is still the likely source of the H7N9 outbreak in China.

Source = BBC NEWS

guardian logo

New bird flu strain ‘more easily caught by humans’ than 2003 outbreak

April 24, 2013

A new strain of bird flu that has killed 22 people in China is “one of the most lethal” of its kind and is more easily transmissible to humans than an earlier strain that has killed hundreds around the world since 2003, a top World Health Organisation (WHO) official has said. The H7N9 virus has infected 108 people in China since it was first detected in March, according to the Geneva-based WHO. Although it is not clear exactly how people have been infected, WHO experts see no evidence so far of the most worrisome scenario – sustained transmission between people. An international team of experts led by the WHO and the Chinese government conducted a five-day investigation in China, but said they were no closer to determining whether the virus could become transmissible between people.

Keiji Fukuda, WHO’s assistant director general for health security, said at a briefing: “The situation remains complex and difficult and evolving. When we look at influenza viruses, this is an unusually dangerous virus for humans.” Fukuda also named the previous H5N1 strain that killed 30 of the 45 people infected in China between 2003 and 2013. Although the H7N9 strain in the current outbreak has a lower fatality rate to date, he added: “This is definitely one of the most lethal influenza viruses that we’ve seen so far.” Fukuda stressed that the team was still at the beginning of its investigation and that “we may just be seeing the most serious infections” at this point. The team of experts said what was mystifying about the latest virus was the absence of visible illness in poultry, “making it harder to track and control”.

Fukuda also said that based on the evidence, “this virus is more easily transmissible from poultry to humans than H5N1”, which has killed 371 people globally since 2003. Ho Pak-leung, an associate professor in the department of microbiology at the University of Hong Kong, noted in the British Medical Journal that in the two months since it was first detected, the H7N9 flu had already resulted in almost twice as many confirmed infections in China as H5N1 caused there in a decade. Besides the initial cases of H7N9 in and around Shanghai, others have been detected in Beijing and five provinces. Samples from chickens, ducks and pigeons from poultry markets have tested positive for the H7N9 virus, but those from migratory birds have not, said Nancy Cox, director of the influenza division at the US Centers for Disease Control and Prevention.

“At least we can now understand the likely source of infection is poultry,” Cox said. The experts also looked at poultry samples from farms but found nothing, said Malik Peiris, a clinical virologist at the University of Hong Kong. Liang Wannian, the director general of the office of health emergency at the National Health and Family Planning Commission, warned that more sporadic cases would probably emerge “before the source of infection has been completely confirmed and effectively controlled”. There has been a “dramatic slowdown of cases” in the commercial capital of Shanghai, which has recorded most of the deaths, said Anne Kelso, the Melbourne-based director of the WHO Collaborating Centre for Reference and Research on Influenza. “This is very encouraging at this stage of the outbreak,” she said.

After Shanghai closed down its live poultry markets in early April, “almost immediately there was a decline in detection of new cases”, Kelso said. “The evidence suggests that the closing of the live poultry markets was an effective way to reduce the risks of infection of the H7N9 virus,” she said. Even so, the WHO’s China representative, Michael O’Leary, issued figures last week showing that half of the patients analysed had no known contact with poultry.

Source = The Guardian

New England Journal of Medicine

Preliminary Report: Epidemiology of the Avian Influenza A (H7N9) Outbreak in China

The first identified cases of human infection with a novel influenza A (H7N9) virus occurred in eastern China during February and March 2013 and were characterized by rapidly progressive pneumonia, respiratory failure, acute respiratory distress syndrome (ARDS), and fatal outcomes.1 We analyzed available data from field investigations to characterize the descriptive epidemiology of laboratory-confirmed cases of avian influenza A (H7N9) virus infection in humans reported to the Chinese Center for Disease Control and Prevention (China CDC) as of April 17, 2013. In this report, we summarize the preliminary findings of case investigations and follow-up monitoring of close contacts of persons with confirmed cases of H7N9 virus infection who have been identified to date. This is an ongoing investigation.

Identification of Cases

Suspected cases of H7N9 virus infection were identified through the Chinese surveillance system for pneumonia of unexplained origin, which was established in 2004.4 Beginning on April 3, 2013, enhanced surveillance was implemented for suspected cases of H7N9 virus infection among persons with mild or moderate illness.5 Persons with suspected cases of H7N9 virus infection with mild or moderate illness were identified from the Chinese sentinel surveillance system for influenza-like illness, which has been described previously.6 Once each suspected case of H7N9 virus infection was identified, the local CDCs, including prefecture and provincial CDCs, conducted the initial field investigations and obtained respiratory specimens, which were shipped to the National Influenza Center of the China CDC in Beijing for H7N9 laboratory testing. A field investigation team comprising staff members of the China CDC and or local CDC conducted field investigations of the confirmed cases of H7N9 virus infection.


Epidemiologic Characteristics of Confirmed Cases

From March 25 through April 17, 2013, respiratory specimens from 664 hospitalized patients with pneumonia of unexplained origin were tested, and 81 patients (12.2%) were confirmed to be infected with the H7N9 virus. Of 5551 respiratory specimens obtained from outpatients with an influenza-like illness through the sentinel surveillance system for influenza-like illness, 1 (0.02%) tested positive for the H7N9 virus. As of April 17, 2013, a total of 82 laboratory-confirmed cases of H7N9 virus infection and 2 suspected cases had been identified cases were identified in the following provinces: Shanghai (31 confirmed cases and 1 suspected case), Zhejiang (25 confirmed cases), Jiangsu (20 confirmed cases and 1 suspected case), Anhui (3 confirmed cases), Henan (2 confirmed cases) and Beijing (1 confirmed case). The median age of patients with confirmed H7N9 virus infection was 63 years (range, 2 to 89); 38 cases (46%) occurred in persons 65 years of age or older, and 2 (2%) were in children younger than 5 years of age, both of whom had clinically mild upper respiratory illness (see Figure S1 in the Supplementary Appendix for the age distribution). Most confirmed cases occurred in males (73%), 84% of the case patients were urban residents, and 54 of 71 patients with available data (76%) had underlying medical conditions.

Geographic Distribution of 82 Confirmed and 2 Suspected Cases

Among 46 of 54 case patients with sufficient data for a more specific classification of underlying conditions, 40 (87%) were considered to be at increased risk for influenza complications owing to age (<5 years or ≥65 years) or prevalence of certain underlying medical conditions.9 Four of the patients with confirmed cases (5%) worked as poultry workers: 3 slaughtered poultry at a live poultry market, and 1 transported live poultry.

A total of 81 of 82 patients with confirmed H7N9 virus infection (99%) were hospitalized. Among the 51 patients with confirmed cases for whom data were available, isolation precautions were instituted for 33 (65%) in an intensive care unit (ICU) because of severe lower respiratory tract disease. As of April 17, a total of 17 patients with confirmed H7N9 virus infection (21%) and 1 patient with suspected infection had died of acute respiratory distress syndrome (ARDS) or multiorgan failure, and 60 patients with confirmed cases and 1 with a suspected case remained critically ill; 4 with clinically mild cases had been discharged from the hospital, and 1 pediatric patient had not been admitted to the hospital. Among 82 confirmed cases of H7N9 virus infection, 7 (9%) were confirmed by means of virus isolation, 2 (2%) by means of serologic testing, and 73 (89%) by means of nucleic acid detection. Viral culture of 73 respiratory specimens that were confirmed as positive by means of real-time reverse-transcriptase–polymerase-chain-reaction (RT-PCR) assays and diagnostic testing of specimens from suspected cases are ongoing.


An epidemiologic study of 82 confirmed cases of H7N9 virus infection in China among persons with illness onset during the period from February through April 17, 2013, indicates that the infection affected persons in a wide age spectrum and caused severe lower respiratory tract illness. To date, the mortality is 21%, but since many of patients with confirmed H7N9 virus infection remain critically ill, we suspect that the mortality may increase. Except for one family cluster with 2 confirmed cases, patients with confirmed H7N9 virus infection were epidemiologically unrelated and were identified in six areas of China. Most of the patients with confirmed H7N9 virus infection were considered to be at increased risk for complications from influenza owing to age (<5 years or ≥65 years; median age of patients with confirmed cases, 63 years) or the prevalence of certain underlying medical conditions.

Human infections with influenza A (H7) viruses have been reported sporadically and are usually associated with exposures to poultry.10-12 Previous human cases of H7 virus infection have been characterized by mild illness (conjunctivitis or uncomplicated influenza) or moderate illness (lower respiratory tract disease) that results in hospitalization.10,11,13,14 Only one fatal case of H7 virus infection has been reported previously; that case occurred in an adult with a highly pathogenic avian influenza A (H7N7) virus infection.15 Many of the confirmed H7N9 case patients had critical and fatal illness, suggesting that the H7N9 virus is more virulent in humans than are other H7 viruses. The H7N9 case fatality proportion to date is lower than that for reported cases of H5N1 virus infection.16 However, early surveillance for H7N9 cases was focused on case finding for severe lower respiratory tract illness, and since April 3, expanded testing of outpatients with influenza-like illness has identified some mild cases of illness with H7N9 virus infection. Enhanced surveillance for less severe illness with H7N9 virus infection will help to determine the clinical spectrum of the illness and the total number of cases of H7N9 symptomatic illness and to inform an understanding of the true case fatality proportion. Since this H7N9 virus appears to have emerged recently to infect humans, population immunity is expected to be low, and persons of any age may be susceptible to infection.

Although the source of the H7N9 virus infection in patients with confirmed cases who had exposure to animals cannot be verified without extensive H7N9 testing of animals, we suspect that it is likely to be infected poultry; additional studies are needed. No animal outbreaks were identified in the areas with confirmed H7N9 cases, but 77% of cases with available data occurred in patients who had exposure to live animals such as poultry or swine, including during visits to live animal markets. This raises the possibility of zoonotic H7N9 virus transmission from healthy-appearing swine or poultry to humans through direct or close contact or through exposure to environments that are contaminated with infected swine or poultry. For example, visiting a live poultry market, where avian influenza A viruses can be maintained and amplified, has been identified as a risk factor for H5N1 virus infection in Hong Kong17 and urban China.18,19 However, case–control studies are needed to identify risk factors for H7N9 virus infection. Until the source of H7N9 virus infection is known, implementation of control measures at live poultry markets, such as a ban on the selling of live poultry in market stalls or even market closure, poultry culling, and market disinfection — measures that have been taken to control the spread of H5N1 virus — may be considered in order to help control potential zoonotic transmission of H7N9 virus.

Follow-up prospective investigations of close contacts of patients with confirmed H7N9 virus infection have not conclusively established human-to-human H7N9 transmission of the virus from one confirmed case to another to date. However, in two family clusters, limited human-to-human transmission of H7N9 virus after close, prolonged, unprotected contact with a symptomatic patient with suspected H7N9 virus infection remains a possibility, because specimens were not available for H7N9 testing from patients with suspected cases; one patient with a suspected case died before a specimen could be obtained, and H7N9 testing of the other patient with a suspected case is still ongoing. Similar family clusters of H5N1 cases that occurred after common poultry exposures or limited human-to-human transmission have been identified.7,20,21 Paired serum samples are being obtained during the acute and convalescent stages of illness from contacts of case patients for further assessment of the potential for secondary human-to-human H7N9 virus transmission, including the identification of asymptomatic infections. Although the risk of human-to-human transmission of H7N9 virus appears to be low, the actual risk is currently unknown, and the Chinese national guidelines recommend implementing control measures, such as prompt isolation of the patient, active monitoring of close contacts, and implementation of standard, contact, and droplet precautions by health care personnel in hospitals. In addition, national guidelines recommend that antiviral treatment with oseltamivir should be administered as soon as possible in patients with suspected or confirmed cases of H7N9 virus infection.

The median time from the onset of illness to hospitalization among the 81 of 82 patients with confirmed H7N9 virus infection for whom data on hospitalization were available was 4.5 days, and the median time from the onset of illness to the development of ARDS among the 19 case patients with ARDS (out of 40 patients for whom data on ARDS were available) was 8 days; the corresponding median times among patients with H5N1 virus infection were 7 days and 7.5 days.22 The median duration from the onset of illness to death among the 17 persons with confirmed cases who died was 11 days. The initial findings suggest that H7N9 virus infection can cause critical illness and fatal disease and may affect persons in a wider age range than the H5N1 virus has in China to date (Figure S1 in the Supplementary Appendix). Patients with confirmed cases received oseltamivir antiviral treatment a median of 6 days after the onset of illness (median before April 3, 9 days), probably owing to delayed suspicion of influenza. Retrospective observational studies of influenza A (H1N1)pdm09 and H5N1 virus infections suggest that early oseltamivir treatment probably has the greatest clinical benefit but that starting treatment up to 5 days after the onset of illness may still reduce the risk of critical illness and death.23-27 Preliminary data suggest that the H7N9 viruses isolated from humans and analyzed to date are resistant to adamantane antiviral agents and are susceptible to neuraminidase inhibitors. Early clinical suspicion of H7N9 virus infection and early administration of oseltamivir may help to reduce the severity of the disease.

Our study had several limitations. First, we did not collect detailed information from all patients on exposures, such as the times, frequency, intensity, and duration of exposures. Information on exposures is useful for estimating the incubation period after possible exposure to animals or live-animal markets and for evaluating the risk factors for H7N9 virus infection. Second, we may not have identified all the close contacts of case patients and were not able to conduct active follow-up of all contacts. As of April 17, 2013, complete follow-up data were not available for some of the close contacts. Third, we did not have a standard protocol and questionnaire to collect information from all contacts of the first 82 patients with confirmed cases. However, the China CDC has issued a guideline and protocol for field investigations of case patients and close contacts and since April 1 has provided training for personnel at all 31 provincial CDCs. This will help ensure standard data collection. Fourth, specimens were not available for H7N9 testing from some patients with suspected cases. Clinical outcomes in the 82 patients with confirmed H7N9 virus infection are reported as of April 17, 2013, and 60 case patients remain hospitalized. Paired serum samples have not been obtained from some of the contacts; no serologic testing results are available at this time, and given the fact that it is early in the investigation, more time is needed to allow for a humoral immune response in serum obtained during the convalescent period and to allow time for serologic testing to be performed.

In summary, a novel influenza A (H7N9) virus has caused severe and fatal illness in persons in six different areas of China to date. Some clinically mild cases have been identified since the surveillance was widened, suggesting that there is a wide clinical spectrum of H7N9 virus infection. The initial epidemiologic findings suggest that most confirmed H7N9 cases were epidemiologically unrelated. Follow-up investigations of contacts of patients with confirmed H7N9 virus infection suggest that the risk of secondary H7N9 virus transmission, including to health care personnel, is low at this time. However, in two family clusters that include persons with confirmed H7N9 virus infection and persons with epidemiologically linked suspected cases, limited nonsustained human-to-human H7N9 virus transmission could not be ruled out and may have occurred among blood-related family members. Enhanced surveillance for severe and mild human illness with H7N9 virus infection is needed to determine the clinical spectrum of the infection and the total number of symptomatic H7N9 infections. Case–control studies to identify risk factors and continued investigations of case patients and their contacts are indicated. Data from investigations of potential animal and environmental sources are urgently needed to inform public health control measures.

Source = New England Journal of Medicine


New bird flu strain called ‘one of most lethal’ viruses baffles scientists

April 24, 2013

A new bird flu strain that has sickened more than 100 and killed 22 in China is “one of the most lethal” of its kind, and has now spread to another country, according to the World Health Organization (WHO). A 53-year-old Taiwan businessman contracted the H7N9 strain of bird flu while travelling in China, Taiwan’s Health Department said Wednesday. This is the first reported case outside China’s mainland.  The man was hospitalized after becoming ill three days after returning from Suzhou on April 9, Health Department Minister Wen-Ta Chiu told a news conference. Chiu said the patient was diagnosed with the H7N9 virus and was in serious condition. Chiu said Taiwan will take appropriate measures, including opening a special out-patient clinic for H7N9 cases.

The Centers of Disease Control and Prevention is keeping a close eye on this virus, which may be resistant to some antibiotic drugs. The CDC received another sample of the virus from China this week, and Mike Shaw, who works at the CDC’s flu lab, said they found certain mutations of the virus, which had they mutated further, would have been rendered ineffective against antivirals, like Tamiful and Relenza.  Dr. Joseph Bresee, a flu expert at the CDC, said it is possible the flu is being transmitted from person to person, but it’s not yet been 100 percent confirmed. When two or three members of a household become sick with the same virus, it’s hard to know if they all acquired it from an infected bird they were exposed to, or if they passed the virus between them, Bresee said.

However, at this point, it’s not clear how exactly people are being infected. Experts maintain there is no evidence of sustained transmission between people. An international team of scientists led by the WHO and Chinese government spent five days in China investigating – – but were not able to determine if the virus was actually spreading between people. The CDC is racing to produce a vaccine for this new strain of bird flu, but it’s still several months out, and officials said it’s difficult to determine if the vaccine would even work. “The situation remains complex and difficult and evolving,” said Keiji Fukuda, the WHO’s assistant director-general for health security. “When we look at influenza viruses, this is an unusually dangerous virus for humans.” Fukuda said that although the current outbreak has a lower fatality rate than the previous type of bird flu, “this is one of the most lethal influenza viruses that we’ve seen so far.”

Source = FOX NEWS


Background and summary of human infection with influenza A(H7N9) virus– as of 5 April 2013

In the past few weeks, WHO has received from China reports of human infection with influenza A(H7N9) virus. The influenza A(H7N9) virus is one subgroup among the larger group of H7 viruses, which normally circulate among birds.

Human infections with other subgroups of H7 influenza viruses (H7N2, H7N3, and H7N7) have previously been reported in the Netherlands, Italy, Canada, United States of America, Mexico and the United Kingdom. Most of these infections occurred in association with poultry outbreaks. The infections mainly resulted in conjunctivitis and mild upper respiratory symptoms, with the exception of one death, which occurred in the Netherlands.

These recent reports from China are the first cases of human infection with H7N9 viruses.


The reported laboratory-confirmed cases have come from several different provinces in eastern China and are not known to be linked. All patients so far have been severely ill, and some have died (for the latest information on cases and outcomes, see Disease Outbreak News.

Two family clusters have been reported. Beyond these two clusters, no cases have been reported among contacts or in health care workers associated with confirmed cases.

The source of infection and the mode of transmission are currently unknown. No association with outbreaks of disease among animals or clear exposure to animals has been established. Some of the confirmed cases had contact with animals or with environments in which animals were located. The virus has been found in a pigeon in a market in Shanghai. The possibility of animal-to-human transmission is being investigated, as is the possibility of human-to-human transmission. The family cluster raises the possibility of human-to-human transmission, but two of the cases in that cluster have not been laboratory confirmed and there is no other evidence pointing toward sustained transmission among people.

Clinical presentation

The main clinical feature among most patients is respiratory diseases resulting in severe pneumonia. Symptoms include fever, cough and shortness of breath. Patients have required intensive care and mechanical ventilation. Information is, however, still limited about the full spectrum of disease that this infection might cause.


The HA gene is genetically distinct from the HA gene of other H7 viruses. The six internal genes are derived from influenza A(H9N2) viruses circulating in birds in eastern Asia. The NA gene is similar to the NA genes from influenza A(H11N9) viruses detected in birds in previous years.
We do not know why cases of influenza A(H7N9) virus infection are being detected now , as we do not know how these persons were infected. Sequence analyses have shown that the genes of the influenza A(H7N9) viruses from the first human cases in China are of avian (bird) origin. However, these genes also show signs of adaption to growth in mammalian species. These adaptations include an ability to bind to mammalian cell receptors, and to grow at temperatures close to the normal body temperature of mammals (which is lower than that of birds).


Laboratory testing conducted in China has shown that the influenza A(H7N9) viruses are sensitive to the anti-influenza drugs known as neuraminidase inhibitors (oseltamivir and zanamivir). When these drugs are given early in the course of illness, they have been found to be effective against seasonal influenza virus and influenza A(H5N1) virus infection. There is no experience yet with the use of these drugs for the treatment of H7N9 infection.


No vaccine for the prevention of influenza A(H7N9) infections is currently available, although viruses have already been isolated and characterized from the initial cases. The first step in development of a vaccine is the selection of candidate viruses that could go into a vaccine. WHO, in collaboration with partners, will continue to characterize available influenza A(H7N9) viruses to identify the best candidate viruses. These candidate vaccine viruses can then be used for the manufacture of vaccine should this become necessary.

While the source of infection and the mode of transmission have not yet been determined, it is prudent to follow good hygiene practices to prevent infection. For advice on infection prevention, contact with animals and food preparation, see: http://www.who.int/influenza/human_animal_interface/faq_H7N9/en/. Guidance for infection prevention and control in health care settings is available at http://www.who.int/csr/resources/publications/swineflu/WHO_CDS_EPR_2007_6/en/index.html.

WHO recommendations

Based on the current situation and available information, WHO advises the following:

• When laboratories testing for influenza viruses detect an influenza A virus by RT-PCR assays using primers for the conserved M genes and then find that tests using currently available H1, H3 and H5 primers are negative, such unsubtypable influenza A viruses should be sent urgently to a WHO Collaborating Centre for further analysis (see http://www.who.int/influenza/gisrs_laboratory/collaborating_centres/en/).
• When a laboratory or Member State finds such an unsubtypable influenza A virus, the finding should be reported to WHO through the International Health Regulations national focal point as is required under the IHR.
• The same surveillance strategy applies as for human infections with highly pathogenic avian influenza A (H5N1) virus.
• Clinicians and laboratory specialists should consider the possibility of human infection with influenza in any person presenting with severe acute respiratory disease.
• Clinicians are reminded of standard guidance for infection control and contact tracing around such cases.
• Standard guidance should also be applied for vigorously investigating clusters of severe respiratory infections and such infections in health care workers who have been caring for patients with severe acute respiratory disease.
WHO does not advise special screening at points of entry with regard to this event nor does it recommend that any travel or trade restrictions be applied.

Source = WHO

France 24

Taiwan confirms first H7N9 bird flu case outside China

AFP – Taiwan on Wednesday reported the first case of the H7N9 bird flu outside of mainland China. The 53-year-old man, who had been working in the eastern Chinese city of Suzhou, showed symptoms three days after returning to Taiwan via Shanghai, the Centers for Disease Control said, adding that he had been hospitalised since April 16 and was in a critical condition.

Source = France 24

New Scientist

China bird flu may be two mutations from a pandemic

April 10, 2013

In China, nine people have died and more than 20 are seriously ill in the latest outbreak of bird flu, H7N9. And there are fears that the death toll could rise much higher because the virus already has three of the five mutations that we know could allow another bird flu, H5N1, to spread between mammals. No one knows for sure if the five mutations discovered last year by Ron Fouchier and colleagues at Erasmus Medical Center in Rotterdam, the Netherlands, will do the same thing in H7N9. But we do know that some of the mutations helped viruses from three other flu families go pandemic. For the moment, Chinese authorities tracing contacts of known cases say there is no evidence yet that the infection has spread between humans. Most recent pandemic viruses have been hybrids of bird and mammalian flu, and therefore relatively mild because mammalian flu tends to be less severe in people than bird flu. Pure bird flu viruses, like H5N1 and H7N9, are potentially more dangerous. The most lethal pandemic we know of, which spread across the world in 1918, was a pure bird flu that acquired mutations that allowed it to spread in humans. Virologists fear H7N9 could be doing that.

H7N9 might be unusually severe: it carries a mutation thought to promote deep lung infection, which is also in H5N1, the 1918 flu, and severe cases of the 2009 pandemic. But two known cases of H7N9 only show mild symptoms, so the Chinese authorities are trying to establish how often it makes people seriously ill, in order to estimate the number of unreported mild cases, and therefore the total number of human cases there have already been.  As for H5N1, despite spreading widely in birds in recent years, it has not evolved the ability to spread readily between mammals. Fouchier’s work – which came under fire because of fears that it would allow bioterrorists to engineer an H5N1 pandemic – shows that, in principle, it can spread between ferrets, and with no obvious loss of virulence. To get transmissible H5N1, Fouchier first had to prime the virus with three mutations known to adapt bird flu to mammals, then allow the virus to evolve the other requisite mutations while infecting the ferrets: as few as two more appeared to be needed.

Two of the three deliberately added mutations allow the HA surface protein from bird flu in the H5, H2 and H3 families to bind to cells in mammals’ noses. This is what allowed flu viruses carrying HA proteins from H2 and H3 bird flu to cause pandemics in 1957 and 1968. The pandemic virus that broke out in 1918 – from the H1 family – had similar mutations with the same effect. Such binding mutations have never been seen in wild H5N1 – but H7N9 already has one of the two. If H7N9 can bind to mammalian cells, it could adapt even further to mammals, just as Fouchier’s primed H5N1 did in his ferret experiments. We do not yet know for certain that the mutation has the same effect in H7 as in the other flu families, but researchers are gearing up to do the experiments.

Source = New Scientist

ABC News

Bird Flu Crosses Strait to Taiwan

A Taiwanese man has contracted a deadly strain of bird flu once confined to mainland China, health officials said today. The man, 53, is thought to have imported the H7N9 virus to his native Taiwan after travelling to China’s Jiangsu Province, where bird flu has sickened at least 24 people and killed three, according to the Chinese Center for Disease Control and Prevention. He is said to be in “severe condition.” The latest case has lifted the tally of virus victims to 109, 22 of whom have died, according to the World Health Organization. It has also flamed fears that the deadly virus could spread beyond East Asia. “Given the extent of global travel, I expect that we will see cases in the United States,” ABC News chief health and medical editor Dr. Richard Besser said. “It’s so important that people who become ill tell their doctors if they have been traveling.”

The Taiwanese man developed flu symptoms April 12, three days after returning to Taiwan from Shanghai, health officials said. He was hospitalized four days later. But initial tests for H7N9 were negative, with official confirmation from Taiwan’s National Influenza Center coming more than two weeks after his trip April 24. “Physicians are once again reminded to report suspected cases to the health authority within 24 hours of detection according to the relevant regulation,” the Taiwanese CDC said in a statement, noting that suspected cases with severe respiratory infections should be hospitalized in isolation. The H7N9 virus is thought to pass from birds to humans. But many of its victims, including the Taiwanese man, reported no contact with birds, and few birds are testing positive for the disease. “There are so many unanswered questions about this disease,” Besser said. “Could there be another route of transmission? Are some people becoming infected from exposure to infected people?”

Source = ABC News

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