Avian H5N1 influenza: In or out flew-enza?
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ABSTRACT: Highly pathogenic avian influenza (HPAI) has been recognized as a serious viral disease of poultry since 1878. The number of outbreaks of this disease globally has increased in the past 10 years culminating in 2004 with the unprecedented outbreak of H5N1 HPAI involving nine countries in East and South East Asia. Apart from the geographical extent of this outbreak and apparent rapid spread, this epidemic has a number of unique features, among which is the carriage of highly pathogenic AI viruses by asymptomatic domestic waterfowl. When this disease first emerged it was recognized almost simultaneously in a number of countries for the first time. This created considerable concern among both veterinary and public health authorities especially as the virus was also shown to cause fatal disease in humans. This article brings together a range of information on H5N1 HPAI viruses in Asia that were collected by FAO during the past year through field projects and explores possible reasons for the emergence of the disease in late 2003 and early 2004. Key epidemiological features of the disease in different Asian countries are described in an attempt to look for, and where possible, explain similarities and differences. This includes assessment of factors that could have contributed to the spread of the disease. Molecular aspects of the viruses are examined to assess relationships between isolates from different locations and times so as to gain insights into the origins of viruses in various countries. It is apparent that the coincidence and grouping of the reports declaring the outbreaks of HPAI did not truly reflect the time course of disease emergence, which was widespread well before the outbreak. The factors that could have led to a change from infection to emergence of widespread disease in 2003-2004 are discussed. There are still some questions that remain unanswered regarding the origins of the 2004 outbreak. This article does not provide answers to all of these, but brings together what is currently known about these outbreaks and the viruses that have caused them.Annals of the New York Academy of Sciences 11/2006; 1081:153-62. · 4.38 Impact Factor
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ABSTRACT: The pandemic influenza virus of 1918-1919 killed an estimated 20 to 50 million people worldwide. With the recent availability of the complete 1918 influenza virus coding sequence, we used reverse genetics to generate an influenza virus bearing all eight gene segments of the pandemic virus to study the properties associated with its extraordinary virulence. In stark contrast to contemporary human influenza H1N1 viruses, the 1918 pandemic virus had the ability to replicate in the absence of trypsin, caused death in mice and embryonated chicken eggs, and displayed a high-growth phenotype in human bronchial epithelial cells. Moreover, the coordinated expression of the 1918 virus genes most certainly confers the unique high-virulence phenotype observed with this pandemic virus.Science 11/2005; 310(5745):77-80. · 31.20 Impact Factor
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ABSTRACT: The influenza pandemic of 1918-20 is recognized as having generally taken place in three waves, starting in the northern spring and summer of 1918. This pattern of three waves, however, was not universal: in some locations influenza seems to have persisted into or returned in 1920. The recorded statistics of influenza morbidity and mortality are likely to be a significant understatement. Limitations of these data can include nonregistration, missing records, misdiagnosis, and nonmedical certification, and may also vary greatly between locations. Further research has seen the consistent upward revision of the estimated global mortality of the pandemic, which a 1920s calculation put in the vicinity of 21.5 million. A 1991 paper revised the mortality as being in the range 24.7-39.3 million. This paper suggests that it was of the order of 50 million. However, it must be acknowledged that even this vast figure may be substantially lower than the real toll, perhaps as much as 100 percent understated.Bulletin of the history of medicine 02/2002; 76(1):105-15. · 0.59 Impact Factor
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the spring of 1918, the second wave in the autumn (September to
November) and the third wave in the spring of 1919. The second
wave was by far the most virulent and lethal and probably resulted
from the virus acquiring mutations that dramatically improved
its human to human transmission and pathogenic characteristics.
It has not been definitively established that the 1918 influ-
enza pandemic virus was an avian virus that adapted to success-
fully infect humans or whether it may have originated from gene
reassortment (antigenic shift) as was observed in the subsequent
emergence of the 1957 (Asian flu) and 1968 (Hong Kong flu)
flu pandemics.2 Evidence for the avian origins of the 1918 has
been argued based on sequence analysis of amino acid variation
in the polymerase proteins consistent with that of avian-derived
virus sequences.3 The polymerase PB1 gene and the haemagglu-
tinin gene in both the 1957 and 1968 pandemic viruses are also
believed to be of avian origin, acquired by genetic reassortment.
Troubling, perhaps, is the observation that many of the present
circulating pathogenic H5N1 viruses are accumulating similar
amino acid changes in the polymerase protein.
H5N1 viruses have been circulating in poultry certainly since
1996 and possibly for decades.4 Highly pathogenic strains of
H5N1 virus have spread from Asia to Europe and Africa infect-
ing millions of poultry and wild birds. In 1997 in China, a
novel avian influenza virus, H5N1, capable of infecting humans
emerged and has continued to cause human infection and death.
www.landesbioscience.com Bioengineered Bugs 145
Bioengineered Bugs 3:3, 145–146; May/June 2012; © 2012 Landes Bioscience
LEttEr to thE Editor
The recent controversy about the potential dangers of publishing
scientific methodologies on the generation of variants of avian
HIN1 influenza capable of infecting ferrets raises some inter-
esting and relevant issues. One of the central issues is does the
publication of such scientific data offer the potential for the pro-
duction of a bioterrorism agent.
Influenza A virus is a serious human pathogen. The pandemic
influenza outbreak in 1918 (“Spanish flu”) may have killed at
least 50 million people worldwide.1 The WHO estimates that up
to 50% of the world’s population became infected approximating
to a mortality rate of 2–2.5%. In fact, this is almost definitively
an underestimation and progressive studies tends to result in an
upwards revision of mortality estimates. Poor record keeping, loss
of data and probably, in some parts of the world, little documen-
tation of cases account for the difficulty in establishing the total
number of cases. Just how lethal the 1918 virus was can be put in
context when compared to a death rate of approximately 100,000
cases for the combined 1957 and 1968 influenza pandemics. The
1918 flu pandemic came in three waves, the first wave occurred in
Avian H5N1 influenza
In or out flew-enza?
John G. Morgan
department of Microbiology; University college cork; cork, ireland
Correspondence to: John G. Morgan; Email: firstname.lastname@example.org
Submitted: 03/27/12; Accepted: 03/27/12
Perhaps one of the prime concerns relating to the danger of H5N1
transmission and infection of humans is the widely published
mortality rate of 50–60% among people infected with H5N1
(352 deaths in 598 cases).5 Many of these cases have occurred
in developing countries and it is probable that subclinical and
mild H5N1 illness has been under reported and documented. A
recent serological meta-analysis study may be a better indicator,
it estimates that the rate of infection of H5NI is approximately
1–2%, implying that millions of people may have been infected
worldwide and indicating a much lower mortality rate.6
So how dangerous are the ferret transmission studies of
Foucheir and Kawaoka? The authors apparently have introduced
several mutations into the H5 gene of avian H5 viruses and can
demonstrate successful aerosol transmission of H5 viruses in fer-
rets, a well recognised mammalian influenza A animal model.
Ferrets are susceptible to infection but are more likely to suffer
disseminated, multi-organ disease than humans and the muta-
tions required for successful human transmission are likely to dif-
fer to some extent to that of ferrets.
In many ways a number of papers published over the last
decade on the 1918 pandemic virus could be viewed as present-
ing much more significant biohazard potential. In 2005, the
complete sequence of the 1918 H1N1 virus was published and
methodologies describing how virus nucleic acid was recovered
from paraffin-embedded autopsy tissue and from frozen lung tis-
sue.3,7 The study successfully generated all 8 gene segments of the
virus and by a process of reverse genetics produced progeny virus
capable of infecting and inflicting high mortality rates in mice
and high replication rates observed in human bronchial epithelial
cells. This reverse genetic approach has been successfully applied
to many viruses such as Hepatitis C and Norovirus so certainly
the technology is out there in cyberspace. Mutations in haemag-
glutinin required for the successful binding of H5N1 virus to
human sialic acid receptors have also been published.8 Human
and avian influenza A viruses differ in virus receptor recogni-
tion, human viruses preferentially binding to sialic acid-alpha
2,6 galactose receptors and avian viruses to sialic acid-alpha 2,3
galactose receptors.8 An adaption to recognition of the 2,6 galac-
tose receptor is believed to be a requirement for successful infec-
tion of human respiratory tract cells.
As scientists we do need to act in a responsible fashion irre-
spective of the fact that the tabloid press can often sensation-
alise certain scientific findings. In recent years people do appear
to have become very cynical of many scientific advances, often
© 2012 Landes Bioscience.
Do not distribute.
mortality of the 1918-1920 “Spanish” influenza pan-
demic. Bull Hist Med 2002; 78:105-115.
Tumpey TM, Belser J. Resurrecting pandemic influ-
enza viruses. Annu Rev Microbiol 2009; 63:79-98.
Taubenberger JK, Reid AH, Lourens RM, Wang R, Jin
G, Fanning TG. Characterization of the 1918 influenza
virus polymerase genes. Nature 2005; 437:889-893.
Martin V, Sims L, Lubroth J, Kahn S, Domenech J,
Begnino C. History and evolution of HPAI viruses in
southeast Asia. Ann NY Acad Sci 2006; 1081:153-162.
WHO. Cumulative number of conformed human cases
for avian influenza A(H5N1) reported to WHO, 2003-
Wang TT, Parides MK, Palese P. Seroevidence for
H5N1 influenza infections in humans: Meta-analtsis.
Science 2012; 335:1463.
Tumpey TM, Basler CF, Aguilar PV, Zeng H, Solórzano
A, Swayne DE, Cox NJ, Katz JM, Taubenberger JK,
Palese P, García-Sastre A. Characterization of the
reconstructed 1918 Spanish influenza pandemic virus.
Science 2005; 310:77-80.
Yamada S, Suzuki Y, Suzuki T, Le MQ, Nidom CA,
Sakai-Tagawa Y, et al. Haemagglutinin mutations
responsible for the binding of H5N1 influenza A virus-
es to human-type receptors. Nature 2006; 444:378-
146 Bioengineered Bugs Volume 3 issue 3
preferring to choose to look at the potential negative impact of
the discovery. Should we as scientists be concerned about the
public perception of scientists and scientific experimentation?
Public opinion can influence legislators who can in turn influ-
ence funding, particularly government funding, of research. A
not insignificant number of people still believe that the HIV
virus was generated by some sinister forces as a blight on man-
kind. They fail to be convinced that the virus is the progeny of
a simian immunodeficiency virus likely to have evolved to infect
humans sometime in the last 100 years. Indeed there are HIV
seropositive blood samples identified as far back in 1957, only 4
years after the discovery of the structure of DNA and many years
before the development of molecular biology techniques capable
of genetically manipulating viral genomes.
The development of molecular biology methodologies dur-
ing the 1960s and 1970s lead to the “Berg letter” and the sub-
sequent Asilomar Conference in 1975 to examine the biohazard
potential and draw up procedures for the safe handling of recom-
binant DNA molecules. This was an appropriate response by sci-
entists to the emergence of a new technology with far reaching
Should we be performing science that is of a questionable
nature? What are the pros and cons of genetically manipulating
an avian influenza virus to more effectively infect mammalian
species. When do the risks outweigh the benefits? The dangers
associated with the inappropriate use of such information has
been highlighted. Can the generation of H5N1 mutants and sub-
sequent infectivity studies in ferrets greatly advance our knowl-
edge and help predict likely H5N1 viruses capable of infecting
humans? If so, this knowledge should guide us and emphasise the
importance of epidemiological surveillance of emerging H5N1
strains that are naturally accumulating these mutations.
True, there are vaccines that protect against H5N1 and H1N1.
The questions with influenza A vaccines are always, “Is there
enough virus vaccine stockpiled to deal with a pandemic? How
good is its shelf life over an extended period of time and, ulti-
mately, the great unknown? Will it protect (totally or partially)
against an avian strain that may naturally emerge to successfully
infect humans?” Similar considerations can be applied to antivi-
rals like oseltamivir. The incubation period for influenza A infec-
tion is short, the order of days, pandemics can be established in
In light of a number of existing publications on H1N1 and
H5N1, it’s difficult to fully understand the hesitancy to pub-
lish the ferret H5N1 infection papers, but caution is never a bad
thing. Let’s hope the issue can be resolved in a timely manner.
The more likely event is that nature will out. Nature will dic-
tate, by mutation and natural selection, whether some variant in
the present pool of circulating avian H5N1 viruses acquires the
ability to successfully infect humans, and will perform umpteen
natural genetic engineering experiments. Let’s be steadfast in our
monitoring and hope nature doesn’t get it right.
1. Johnson NP, Mueller J. Update the accounts: global