Spanish flu-like virus could emerge from birds.

Bird flu viruses are just a few genetic steps away from the flu virus that caused the deadly 1918 Spanish flu pandemic, a new study shows.

An international team of virologists identified the key genetic components — similar to those in the virus behind the 1918 pandemic — in influenza viruses in wild ducks.

The findings, published in the journal Cell Host and Microbe , suggest that 1918-like pandemic viruses may emerge in the future.

“Because avian influenza viruses in nature require only a few changes to adapt to humans and cause a pandemic, it is important to understand the mechanisms involved in adaptations … so we can be better prepared,” says study lead author Yoshihiro Kawaoka of the University of Wisconsin-Madison.

The Spanish flu killed up to 50 million people across the world in 1918.

Previous genetic analysis indicates the deadly virus was a type of influenza A of avian origin, although this finding is controversial.

Wild birds harbour a large gene pool of influenza A viruses that could cause pandemics, but the likelihood of birds harbouring a virus similar to the 1918 pandemic virus has been unclear.

To assess the risk, the scientists used reverse genetic methods to recreate a virus that differed from that of the Spanish flu by only 3 per cent of the amino acids that make the virus proteins.

In the animals it was tested on, the new virus was less pathogenic than the Spanish flu — but more so than avian flu.

However, the scientists then discovered seven mutations in three virus genes that allowed it to spread as easily as the Spanish flu in ferrets, an animal commonly used in influenza transmission studies.

Consisting of genetic factors already present in wild bird populations, the virus showed that genetic ingredients capable of combining to create a dangerous pathogen that could produce a human pandemic exist in nature.

Surveillance strategies

Kawaoka says the discovery could help scientists develop more effective strategies to combat the emergence of such a disease.

“Research findings like this help us assess the risk of outbreaks and could contribute to routine surveillance of influenza viruses,” he says.

The research also shines light on the bird flu virus’s adaptive mechanisms for spreading to mammals.

A mutation of a protein on the surface of the virus, for example, allows it to cling to an organism’s cells and could increase the virus’s ability to infect human respiratory tracts.

The researchers also discovered that the virus they created reacted to the current vaccine against seasonal flu — which is effective against H1N1 flu responsible for a 2009 pandemic — indicating that the current vaccine could offer protection against a pandemic.

The scientists also noted that the virus was sensitive to oseltamivir, an antiviral medication to prevent and slow the flu.


HK confirms first H7N9 bird flu case

A vendor weighs a live chicken at the Kowloon City Market on 12 April 2013 in Hong Kong. Local authorities have stepped up the testing of live poultry imports from China to include a rapid test for the H7N9 "bird flu" virus

Hong Kong has suspended the import of live chickens from some China farms

  • Hong Kong has confirmed its first case of the new strain of the H7N9 bird flu in a domestic worker from Indonesia.

The worker, 36, recently travelled to Shenzhen in the mainland and came into contact with live poultry. She is in critical condition, officials say.

H7N9 has infected more than 100 people since it emerged earlier this year.

The case in Hong Kong is a sign that the virus may be spreading beyond mainland China, where most infections have been reported, and Taiwan.

The World Health Organization (WHO) had said there was “no evidence of sustained human-to-human transmission”, but also described H7N9 as an “unusually dangerous virus”.

At least 139 human cases of H7N9 have been confirmed, including 45 deaths, WHO says in a statement dated 6 November.

At least one case was confirmed in Taiwan in April.

Dr Ko Wing-man, Hong Kong’s food and health secretary, confirmed the territory’s first H7N9 case late on Monday.

He said that the patient “has a history of travelling to Shenzhen, buying a chicken, slaughtering and eating the chicken”.

“She is now in critical condition at Queen Mary Hospital,” he said, adding that four people in close contact with her were showing signs of flu-like symptoms.

Hong Kong is now on public health alert and has suspended the import of live chickens from some farms across the border with the mainland.

H7N9 is a type of influenza virus that normally circulates among birds and has not until recently been seen in people, the WHO says.

“There is no indication thus far that it can be transmitted between people, but both animal-to-human and human-to-human routes of transmission are being actively investigated,” the organisation adds.

‘Unpredictable pandemics’ warning

The world needs to be prepared for “unpredictable pandemics” from viruses making the leap from animals to people, scientists in Taiwan say.

Their warning follows the first reported case of a common bird flu, H6N1, being detected in a woman, earlier this year.

The patient recovered and no other cases have been detected.

But the Lancet Respiratory Medicine report said “intensive” monitoring of bird flu was needed.

In May 2013, the first human case of an H6N1 bird flu was detected in a woman in Taiwan. One of her neighbours bred ducks, geese and chickens – although the precise source of the infection has not been detected.

Many sub-types of influenza, such as those that cause seasonal flu or the swine flu pandemic, are known to infect people, but H6N1 is not one of them.

The report, by the Centres for Disease Control in Taiwan, said: “The occurrence of a human case of H6N1 infection shows the unpredictability of influenza viruses.


“Our report highlights the need for influenza pandemic preparedness , including intensive surveillance for ever evolving avian influenza viruses.”

Prof Wendy Barclay, from Imperial College London, said these infections may have happened in the past but improved technology had meant this one had been discovered.

She said: ” Is this a truly new thing or are we now just better at seeing it?”

She told the BBC she expected far more of these cases to be reported in the next few years as more hospitals were geared up to look for novel bird flus.

Prof Barclay added: “This is a single case with no evidence of human transmission, but as always we should keep an eye on it and do studies to see how close it is to being able to spread between humans.”

Novartis announces positive clinical trial results for novel H7N9 vaccine.

  • 85% of subjects immunologically protected after receiving second dose of investigational cell culture vaccine when combined with proven MF59® adjuvant

  • Vaccine now in large scale production highlighting rapid response capability of novel FDA licensed cell culture technology

  • 135 confirmed cases and 45 deaths from H7N9 virus since emergence in March according to the World Health Organization.

Novartis announced today interim results from a Phase 1 clinical trial with its proprietary cell culture vaccine for the H7N9 avian influenza virus involving 400 healthy volunteers (18-64 years of age). The data shows 85% of subjects achieved a protective immune response after two doses of the 15 ug MF59 adjuvanted vaccine. Only 6% of subjects achieved a protective response when given two doses of the 15ug un-adjuvanted vaccine. The full data set from the trial will be submitted to a peer-reviewed journal for publication in the near future. 

The vaccine was produced utilizing full-scale cell-culture manufacturing technology, an alternative technology that can significantly accelerate vaccine production versus traditional egg-based methods.[2] Cell-culture technology utilizes a well-characterized mammalian cell line rather than chicken eggs to grow virus strains.[3]

“This rapid response underscores our leadership position in pandemic preparedness” said Andrin Oswald, Division Head, Novartis Vaccines. “Thanks to our investments into innovative production technologies and adjuvants, we are now able to offer a protective solution for a potentially deadly pandemic virus within a few months after the emergence of the H7N9 virus.”

Reports of H7N9 infection first emerged in China in March 2013. Novartis, along with its partners at the Craig Venter Institute, first synthesized the viral strain several days after it was shared with global researchers by the Chinese Centers for Disease Control. Novartis then produced clinical trial lots, began clinical trials in August, and initiated large-scale production in its Holly Springs (NC), USA and Marburg, Germany facilities in October.

Probable person to person transmission of novel avian influenza A (H7N9) virus in Eastern China, 2013: epidemiological investigation.


Objective To determine whether the novel avian influenza H7N9 virus can transmit from person to person and its efficiency.

Design Epidemiological investigations conducted after a family cluster of two patients with avian H7N9 in March 2013.

Setting Wuxi, Eastern China.

Participants Two patients, their close contacts, and relevant environments. Samples from the patients and environments were collected and tested by real time reverse transcriptase-polymerase chain reaction (rRT-PCR), viral culture, and haemagglutination inhibition assay. Any contacts who became ill had samples tested for avian H7N9 by rRT-PCR. Paired serum samples were obtained from contacts for serological testing by haemagglutination inhibition assays.

Main outcomes measures Clinical data, history of exposure before the onset of illnesses, and results of laboratory testing of pathogens and further analysis of sequences and phylogenetic tree to isolated strains.

Results The index patient became ill five to six days after his last exposure to poultry. The second patient, his daughter aged 32, who provided unprotected bedside care in the hospital, had no known exposure to poultry. She developed symptoms six days after her last contact with her father. Two strains were isolated successfully from the two patients. Genome sequence and analyses of phylogenetic trees showed that both viruses were almost genetically identical. Forty three close contacts of both patients were identified. One had mild illness but had negative results for avian H7N9 by rRT-PCR. All 43 close contacts tested negative for haemagglutination inhibition antibodies specific for avian H7N9.

Conclusions The infection of the daughter probably resulted from contact with her father (the index patient) during unprotected exposure, suggesting that in this cluster the virus was able to transmit from person to person. The transmissibility was limited and non-sustainable.


We believe that the most likely explanation for this family cluster of the two patients with novel avian influenza H7N9 virus infection is that the virus transmitted directly from the index patient to his daughter. Firstly, the diagnosis of the two patients was confirmed virologically, and the clinical features―fever, pneumonia with lymphopenia, and rapid progression to acute respiratory distress syndrome—all correspond to the cardinal features of reported cases in humans in China.17 18 Secondly, it was fortuitous for the investigation that the daughter did not visit the markets to buy foodstuffs and cook for the family and had no exposure to animals or history of visiting live poultry markets. She did, however, have prolonged, direct, and unprotected exposure to her father. Thirdly, two strains were isolated successfully from the two patients. Further sequence analysis showed that both possessed high degrees of similarity between nucleotide (99.6%-99.9%) and amino acid (99.0%-100%) sequences. Finally, before this study, A (H7N7) among H7 subtype influenza viruses and H5N1 virus was known to have the ability to transmit from person to person.19 20 21 Animal (ferrets and pigs) experiments indicated that the H7N9 virus possessed the capability to bind to both avian and human receptor and to transmit itself by droplet under certain conditions.22 23

Our findings, however, indicated that the virus has not gained the ability for efficient sustained transmission from person to person. From 14 March, the daughter came into direct contact with the oral secretions of the index patient without any personal protective equipment, contacting the patient at a much higher rate than other individuals in contact with the patient. Similar to other available human strains, the characteristics of the two strains showed no adaptation change in the receptor binding site from the avian 2,3-linked pattern toward the human 2,6-linked pattern of sialic acid receptor.1 7 Phylogenic tree analysis of all eight genomic segments indicated that the two isolates were of avian origin and that there was no reassortment with human or swine influenza viruses.24 2526 Furthermore, no asymptomatic or subclinical infections were identified among 43 close contacts by haemagglutination inhibition testing. Recent studies also indicated that avian H7N9 tends to bind lower pulmonary epithelial cells rather than those of the upper respiratory tract, which makes it difficult to transmit between humans.7

The two patients were blood related. The index patient’s son in law also provided bedside care for the index patient in the mornings and nights between 11 and 13 March without any personal protective equipment. Both biological and serological evidence showed that he was not infected with the H7N9 virus. These findings suggest that potential genetic susceptibility might be one of determinants and that avian influenza viruses, like H5N1, are more easily transmitted between individuals with genetic connection.27 28

The possible source of infection for the index case was likely to be from the live poultry market that the patient used to visit or the six quails that he bought but were slaughtered by the seller in the market one week before illness onset. One strain of avian H7N9 was isolated from environmental samples from the live poultry markets. Visiting a wet poultry market has been identified as a risk factor for human infections.8 9

Important strengths and differences in relation to other studies

With respect to the possible infection period in the second patient, we cannot ascertain when person to person transmission occurred. The most likely period was from 11 to 15 March during the index patient’s admission to hospital before transfer to intensive care, especially the periods between the afternoon of 14 March and the morning of 15 March, when the index patient began to expectorate abundantly. The daughter had direct and close contact with the index case without any protection during this period. During 8-10 March, the daughter provided only conventional care for the index patient, such as taking his temperature. Transmission is unlikely to have occurred during this period as the patient had not yet to start expectoration. Thus, the most likely incubation period was six to seven days (range 6-13 days) based on the daughter’s unprotected exposure to her father. The putative incubation period was a relatively longer than that reported by Cowling and colleagues, who estimated the average incubation period to be around three days based on Weibull model as well as live poultry to human transmission.29 We estimated the incubation period based on person to person transmission and one case in cluster.

Implications of the study

Possible transmission routes include contact while cleaning up infected oral secretions and subsequent inoculation of mucous membranes or the respiratory tract. Some researchers suggested that the daughter might have acquired her infection during the process of washing her father’s diarrhoea-soiled underwear.11 We thought this to be unlikely. Firstly, clinical data showed that the index patient did not develop diarrhoea during course of disease. Secondly, the daughter wore gloves while washing. Thirdly, no nucleic acids specific for avian H7N9 were detected from the faecal samples from the father.

We noted that 39 healthcare workers were identified as close contacts in this cluster, which was a little unusual. Both the two hospitals where the two patients were admitted were general hospitals rather than hospitals specialising in infectious disease. The awareness of personal protection of the healthcare workers was relatively weak. They used common surgical masks instead of N95 masks while providing medical services for the two patients. Another important factor was the relatively long time between the patients’ admission to a clear diagnosis with H7N9 virus infection. After the cluster was identified, infection control measures were initiated to prevent potential nosocomial transmission. Patients were isolated. Healthcare workers were required take standard respiratory and contact protection.

Weaknesses of the study

There are several limitations to our study. Firstly, we could not interview with the two patients as they were both critically ill. Therefore, the possibility that the daughter acquired her infection from the environment or other sources could not be completely ruled out, although we believe that it is less likely. Environmental investigation discovered that in addition to two swans raised by an employee of the property management, there were no other birds or poultry in her living environment. No positive results were detected from the cloacal swab and faecal samples from the two swans. Secondly, the sensitivity of haemagglutination inhibition assay was not satisfied. Thus, subclinical or asymptomatic infections could not be excluded among close contacts. A more sensitive method such as micro-neutralisation assay should be considered in the future. Finally, whole sequence alignment showed that the two isolates from patients were not identical. It is reasonable to expect slight differences between the two strains. Variations of the viral genomes occur constantly because of the high error rate of the viral polymerase. We sequenced viral genomes from the strain from the father that underwent three successive passages using MDCK cell lines. Evolution of the strain might have occurred in vivo because of the long time interval as well as the use of antiviral drugs. A previous study showed that influenza viruses often differ from those present in clinical specimens after isolation in MDCK cell culture as adaptive changes occur during virus transmission from the human host to cells of heterologous origin.30

Unanswered questions and future research

To the best of our knowledge, this is the first report of probable transmissibility of this novel virus from person to person with detailed epidemiological, clinical, and virological data. The importance of an isolated case of such transmission means there is potential for greater human to human transmission. Thus, timely detection as well as rapid investigation and risk assessments of clusters is critically important as the increase in clusters might indicate potential transmissibility of a novel virus.

What is already known on this topic

  • Most cases of novel avian H7N9 occur sporadically
  • Animal experiments indicated that the H7N9 virus can transmit itself by droplet under certain conditions
  • No definite evidence indicates that the novel virus can transmit itself from person to person
  • To our best knowledge, this is the first report of probable transmissibility of the H7N9 virus from person to person with detailed epidemiological, clinical, and virological data
  • Our findings reinforced that the novel virus possesses the potential for pandemic spread

What this study adds


Source: BMJ


Pandemic Influenza Viruses — Hoping for the Road Not Taken.


In the Robert Frost poem “The Road Not Taken,” a traveler recalls a time when his forest path forked and wonders where he would have ended up had he chosen the other path. Some viruses encounter analogous evolutionary divergence points, and they may not all take linear paths to inevitable outcomes.

For instance, a novel avian influenza A (H7N9) virus has emerged in China.1 Because all known pandemic and other human, mammalian, and poultry influenza A viruses have descended from wild-bird viruses, it seems logical that any avian influenza A virus that becomes pandemic must have serially acquired signature mutations known to be associated with circulation in humans. It would follow that mutations distinguishing “avian-like” from “human-like” viruses must be milestones on a fixed evolutionary pathway to potential pandemicity, including mutations affecting the hemagglutinin (HA) receptor–binding domain associated with efficient binding to human epithelial cells, polymerase mutations associated with efficient replication in human cells, and others. The fact that H7N9 isolates have some of these mutations1 has led to predictions of its evolution toward pandemicity.

However, firm scientific evidence for such well-defined linear pathways is lacking. Since 1918, the emergence of four pandemic viruses has been documented, but scientists have found no evidence of a direct mutational mechanism2; conversely, many avian viruses have infected humans and rapidly developed such mutations without becoming pandemic. Rather than being indicators of inevitable pandemic progression, these mutations may simply be markers that any avian influenza virus is likely to develop when it replicates in human cells. In keeping with this interpretation, novel human H7N9 isolates have several “human-like” mutations affecting HA, viral polymerase, and other proteins, whereas temporally and geographically related avian H7N9 isolates do not.1

The critical but currently unanswerable question is whether every avian influenza virus capable of infecting humans can acquire serial pandemic-generating mutations without being limited by structural or functional evolutionary constraints — or whether pandemic viruses are rare entities whose complex gene constellations cannot easily be configured except by rare and still-obscure mechanisms. We do know that humans, who can be easily infected with avian influenza A viruses by experimental challenge, are naturally and repeatedly exposed to and often infected by many such avian viruses without generating pandemics — as evidenced by multiple epidemics and case clusters as well as by serosurveys.3,4

Given the potential daily exposures of millions of humans to various avian influenza viruses, the extreme rarity of new viral adaptation to humans suggests that despite a low species barrier for infection, barriers against productive infection and onward transmission must be exceedingly high. The reason may be that to adapt fully to humans, avian influenza viruses require precisely attuned and mutually cooperating gene constellations, which result from finely balanced polygenic mutations4 that are extremely unlikely to accumulate and survive in preadapted viruses.

Moreover, among the 17 influenza HAs and 10 neuraminidases (NAs) known to exist in nature, only a few subtype combinations — H1N1, H2N2, and H3N2 — have ever, in 95 years of virologic observation, been incorporated into any human-adapted or pandemic influenza A virus. Epidemiologic and archaeserologic evidence arguably extends this HA subtype restriction back to the 1830 and 1889 pandemics,5 supporting the belief that influenza pandemics occur in cycles of H1, H2, and H3 and that this cyclicity is driven by older birth cohorts that retain and newer cohorts that lack high HA-specific population immunity. The apparent HA restriction seems unlikely to be coincidental, since the influenza virus HA genes that have been associated with human pandemic viruses, such as H1 and H2, are not particularly common in avian viruses, and since more common avian influenza subtypes, such as H4 and H6, have never been seen in human-adapted viruses.

If few or none of the millions of avian influenza viruses that continually infect humans ever become pandemic, how do pandemics arise? We know that all pandemic viruses since 1918 descended from the 1918 pandemic founder virus,2,5 having been generated through periodic antigenic shifts, intrasubtypic reassortments, and continual antigenic drift.2 Unfortunately, we do not yet know the origin of the 1918 virus, and phylogenetic and sequence analyses aiming to determine its origin are controversial.

All eight 1918 viral gene segments encode proteins close to the avian influenza A viral consensus sequence, which suggests that they either had a direct avian origin or an evolutionarily brief preliminary period in another host. The relative protection in 1918 of people older than 65, however, suggests that a related virus was circulating after the 1830 pandemic.5 That possibility is important because if the 1918 virus emerged directly from a bird, then any avian influenza A virus, such as H5N1 or H7N9, might be able to do the same. If, in contrast, it emerged through antigenic recycling, as all subsequent pandemic viruses have done, then it is important to recognize that this pattern has not thus far included viruses with other HAs and NAs, such as H5, H7, and N9. But given influenza viruses’ unpredictability, the implications of this historical behavior for H7N9’s likelihood of evolving into a human pandemic virus remains unclear.

Although wholly avian in origin, H7N9 seems to have been generated by a reassortment of wild-duck H7 HA and wild-bird N9 NA genes, with six internal genes from two different H9N2 chicken influenza viruses (Origin of the Novel Avian Influenza A H7N9 Virus.). That H9N2 viruses have been spreading panzootically in poultry and have also infected pigs and humans suggests an inherent capacity to adapt broadly to multiple species. This adaptability is worrisome, because H7N9 viruses might theoretically spread with similar ease to encounter other circulating mammalian-adapted influenza genes that are suitable for reassortment. However, host switching of wild-bird influenza A viruses into poultry typically sets off a mutational pathway divergent from mammalian adaptation, arguably driving any such viruses further away from potential pandemicity.4

Finally, there is remarkable clinical–epidemiologic similarity between H7N9 and H5N1, with the important distinction that since H5N1 is a highly pathogenic avian virus that kills domestic poultry, its movement is more visible than that of H7N9, whose low pathogenicity keeps it hidden until a rare human is infected. In most other respects, H5N1 and H7N9 are alike: many humans have been exposed to both without clinically apparent or immunologically detectable evidence of infection; disease in sporadic human cases has been far more severe than in cases caused by any human-adapted influenza A virus ever encountered (59% and 28% case fatality reported for H5N1 and H7N9, respectively, as of the end of May); the clinical presentation includes bilateral pneumonia progressing to acute respiratory distress syndrome and multiorgan failure; there has been little or no evidence of person-to-person transmission; and rare case clusters (tenuously identified so far in the case of H7N9) suggest common source exposures in genetically related persons.

As with H5N1,3,4 in H7N9 these epidemiologic features may be signatures of a fundamentally poorly adaptable avian virus that nevertheless productively infects those rare humans with unidentified genetic susceptibilities, who are “found” by widespread poultry epizootics that expose large human populations. Conceivably, questions raised by H5N1 and H7N9 will be faced repeatedly as large-scale domestic poultry raising and transport, coupled with exploding human populations, create opportunities for any avian virus that encounters domestic poultry to expose large numbers of humans.

Like every human influenza pandemic and major outbreak in more than a century, H7N9 has left us surprised and puzzled. It is only slightly reassuring that since 1918, we have never seen an influenza pandemic emerge through direct viral mutations alone. But every pandemic emergence seems to be a law unto itself, and we cannot know whether or under what circumstances the highly unusual H7N9 virus might be able to become pandemic. Influenza viruses’ unpredictability renders H7N9 pandemic preparedness essential. Indeed, preparation has already begun, with the goals of developing sensitive and specific diagnostics; determining drug sensitivity; establishing seed viruses, pilot lots, and potency assays for vaccine development; and setting up clinical trials to test appropriate vaccine doses for various demographic groups (children, adults, the elderly).

H7N9’s journey has just begun. We can only hope that the road to a pandemic is the road not taken.


Source: NEJM


Novel Avian-Origin Influenza A (H7N9) Virus in China.

130418094043-china-bird-flu-0418-horizontal-galleryTesting of throat-swab specimens from three patients who died of severe lower respiratory tract disease revealed infection with a novel reassortant H7N9 virus.


Because of the morbidity and mortality associated with H5N1 influenza, avian influenza virus infection in humans has garnered considerable attention. Now, investigators describe the clinical profile of three patients in China who died from complications of severe lower respiratory tract disease caused by a novel reassortant avian-origin influenza A (H7N9) virus.

Two of the patients (one residing in Shanghai, the other in Anhui Province) had been present at a chicken market within 7 days of illness onset; the third (also from Shanghai) had no known exposure to live birds within the preceding 2 weeks. All three patients had “high” fever, cough, and dyspnea, and all of them developed acute respiratory distress syndrome. All also had leukopenia, lymphocytopenia, and ground-glass opacities and consolidation on chest radiography, and two of them manifested rhabdomyolysis. Two patients died within 10 days of hospital admission, and the third one within 20 days.

Throat-swab specimens obtained from the patients were subjected to viral propagation in pathogen-free embryonated chicken eggs and RNA extraction. Real-time reverse-transcriptase polymerase chain reaction, genome sequencing, and phylogenetic analysis revealed that all three patients had been infected with a novel avian-origin influenza A (H7N9) virus.

Comment: On the basis of the findings from these patients, diagnostic tests for the novel reassortant H7N9 viruses have been developed. Public health officials around the world continue to closely monitor this outbreak, which serves as a reminder of influenza viruses’ unique capacity to evolve and cause respiratory tract infections in humans.

Source: Journal Watch Infectious Diseases

FDA Panel Recommends Approval of Adjuvanted Bird Flu (H5N1) Vaccine .

An adjuvanted vaccine against the avian influenza virus (H5N1) has been recommended for approval by an FDA advisory panel, Reuters reported last week.

Another vaccine has already been licensed for H5N1, but the newer vaccine would require much less antigen to be effective because of the presence of the adjuvant. That would make it easier to produce enough doses during an epidemic, according to the report.

Source: Reuters