19 May 2013
On episode #233 of the science show This Week in Virology, Vincent, Rich, Alan and Kathy review aerosol transmission studies of influenza H1N1 x H5N1 reassortants, H7N9 infections in China, and the MERS coronavirus.
You can find TWiV #233 at www.twiv.tv.
17 May 2013
Robert Herriman of The Global Dispatch interviewed me this week on the H1N1 – H5N1 reassortant study that has been in the headlines:
There was much written concerning the research published earlier this month in Science, where researchers from China’s Harbin Veterinary Research Institute reported creating an avian H5N1 (highly pathogenic) and pandemic 2009 H1N1 (easily transmissible) hybrid, that according to them, achieved airborne spread between guinea pigs.
Read the rest of the article at The Global Dispatch.
16 May 2013
This discussion of West Nile virus was recorded at the headquarters of the American Society for Microbiology during a “Microbes After Hours” event on May 6, 2013. The speakers are Dr. Lyle Petersen Lyle R. Petersen, M.D., M.P.H., director of the Division of Vector-Borne Diseases at CDC, and Dr. Roberta DeBiasi, MD, FIDSA, Associate Professor of Pediatrics at George Washington University School of Medicine, Acting Chief and Attending Physician in the Division of Pediatric Infectious Diseases at Children’s National Medical Center, and investigator at Children’s Research Institute in the Center for Translational Science in Washington, D.C.
MWV Episode 70 – Microbes After Hours – West Nile Virus from microbeworld on Vimeo.
I joined Buddhini Samarasinghe, Scott Lewis, Tommy Leung, and William McEwan for a discussion of the avian influenza H5N1 virus transmission experiments done in ferrets.
12 May 2013
On episode #232 of the science show This Week in Virology, Vincent meets up with Roberto, Reuben, Lou, and Leslie at the University of Minnesota to talk about their work on HIV-1, APOBEC proteins, measles virus, and teaching virology to undergraduates.
You can find TWiV #232 at www.twiv.tv.
On episode #231 of the science show This Week in Virology, Vincent meets up with Amit, Lan, and Ian to discuss their discovery of hepaciviruses and pegiviruses in bats and rodents.
You can find TWiV #231 at www.twiv.tv.
29 April 2013
I joined Buddhini Samarasinghe and Scott Lewis on a Science Sunday Hangout on Air to talk about my career in virology: how I came to be interested in viruses, and what goes on in my laboratory. You can find hangouts and more at the ScienceSunday community.
28 April 2013
On episode #230 of the science show This Week in Virology, Vincent, Rich, Alan and Kathy review H7N9 infections in China, the debate over patenting genes, and receptor-binding by ferret-transmissible avian H5 influenza virus.
You can find TWiV #230 at www.twiv.tv.
Results of a study of four patients in Zhejiang, China, who developed influenza H7N9 virus infection suggests sporadic poultry-to-human transmission:
We diagnosed avian influenza A H7N9 in all four patients (who were epidemiologically unlinked), two of whom died and two of whom were recovering at the time of writing. All patients had histories of occupational or wet market exposure to poultry. The genes of the H7N9 virus in patient 3′s isolate were phylogenetically clustered with those of the epidemiologically linked wet market chicken H7N9 isolate. These findings suggest sporadic poultry-to-person transmission.
The four patients had occupational contact with poultry: one was a chef, one slaughtered and cooked live market poultry, and two bought live market poultry. Each had contact with poultry 3-8 days before onset of disease, and all were positive for influenza H7N9 virus by polymerase chain reaction of sputum or throat swab samples (virus was cultured from three of the four patients). Two of five pigeons and four of 20 chickens from two different wet markets were also positive for influenza H7N9 virus. Sequence analysis of virus recovered from patient 3 revealed that the HA and NA genes are nearly identical with those of two viruses isolated from epidemiologically linked chickens (1673 of 1683 bases for HA, 1394 of 1398 bases for NA).
While these H7N9 infections might have been acquired from poultry, the origin of other infections in different areas of China (>100) is unclear. According to the Ministry of Agriculture, as of 26 April 2013, only 46 of the 68,060 samples collected from poultry markets, habitats, farms and slaughterhouses across the country have tested positive for H7N9 virus, and none of these positive samples have been from poultry farms.
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Influenza H5N1 x H1N1 reassortants: ignore the headlines, it’s good science
7 May 2013
Those of you with an interest in virology, or perhaps simply sensationalism, have probably seen the recent headlines proclaiming another laboratory-made killer influenza virus. From The Independent: ‘Appalling irresponsibility: Senior scientists attack Chinese researchers for creating new strains of influenza virus’; and from InSing.com: ‘Made-in-China killer flu virus’. It’s unfortunate that the comments of several scientists have tainted what is a very well done set of experiments. Let’s deconstruct the situation with an analysis of the science that was done.
It is known that avian influenza H5N1 viruses can occasionally infect but not transmit among humans, while the 2009 pandemic H1N1 virus (which continues to circulate) readily transmits from person to person. The investigators asked whether reassortants of the two viruses – which could arise in nature – might confer transmissibility to H5N1 virus. To answer this question they produced 127 different reassortants of the two viruses, and tested their ability to transmit by aerosol among guinea pigs. The latter have been used for transmission studies on influenza, notably to understand the seasonality of infection. Ferrets have been more famously used for influenza virus transmission studies.
Rather than describe the results, I’ve made an illustration that shows what I believe to be the most important conclusions of the study (click for a larger version):
The H5N1 virus (red RNAs) is not transmissible among guinea pigs, while the H1N1 virus (green RNAs) has highly efficient transmission. Exchange of the H5N1 RNA coding for PA or NS from H1N1 produces a highly transmissible virus. Exchange of the H5N1 RNA coding for NA or M produces a less efficiently transmitted virus. These are interesting and novel findings. It will be of great interest to determine how the PA, NS, NA, or M genes mechanistically enhance aerosol transmission. This is important information because our understanding of the determinants of transmission is very poor.
All the reassortant viruses shown in the figure have the H5 HA; when only the H1 of the H1N1 virus was substituted with the H5 HA, the reassortant virus transmitted efficiently among guinea pigs. In ferrets the H5 HA is not compatible with aerosol transmission. Therefore guinea pigs are clearly different from ferrets with respect to the determinants of transmissibility.
I cannot understand why some scientists have called these experiments ‘appallingly irresponsible’ and of no scientific use. I can only assume that they are not familiar with the literature on viral transmission and do not appreciate how the results advance our understanding of the field. It also seems irresponsible to predict that these viruses, should they escape from the laboratory, could kill millions of people. If you accept guinea pigs as a predictor of human pathogenicity – which I do not – then there is no reason for fear because none of the reassortants were lethal. I do not believe that any animal model predicts what will occur in humans, and so I am even less concerned about the safety of these experiments. I firmly believe that laboratory-constructed viruses do not have what it takes to be a human pathogen: only viral evolution in nature can produce the right combination of RNA segments and mutations. I also believe that scientists are quite responsible when it comes to safe handling of pathogens. If we worry about every type of transmission experiment involving influenza H5N1 virus, we will never make progress in understanding why this virus does not transmit among humans. The moratorium on H5N1 transmission research is over; let’s move beyond the sensational headlines and get back to the science.
In summary, I believe that these are well designed experiments which show that single RNA exchanges with H1N1 virus can produce an H5N1 virus that transmits via aerosol among guinea pigs. The relevance of these findings to humans is not known; nevertheless understanding how the individual viral proteins identified in this study enhance transmission may be mechanistically informative. I believe that the news headlines depicting these experiments as irresponsible and dangerous are based on uninformed statements made by scientists who are not familiar with the literature on influenza virus transmission. I wonder if they even read the paper in its entirety before making their comments.
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