̽��ֱ�� of Cambridge - Nicola Lewis

Threat of novel swine flu viruses in pigs and humans

Anonymous — Wed, 27 Apr 2016 11:21:37 +0000

While swine flu viruses have long been considered a risk for human pandemics, and were the source of the 2009 pandemic H1N1 virus, attention has recently turned to the transmission of flu viruses from humans to pigs.

"Once in pigs, flu viruses from humans continue to evolve their surface proteins, generically referred to as antigens, resulting in a tremendous diversity of novel flu viruses that can be transmitted to other pigs and also to humans," explains first author Nicola Lewis from the ̽��ֱ�� of Cambridge.

"These flu viruses pose a serious threat to public health because they are no longer similar enough to the current human flu strains for our immune systems to recognise them and mount an effective defence. Understanding the dynamics and consequences of this two-way transmission is important for designing effective strategies to detect and respond to new strains of flu."

Humans and pigs both experience regular outbreaks of influenza A viruses, most commonly from H1 and H3 subtypes. Their genetic diversity is well characterised. However, the diversity of their antigens, which shapes their pandemic potential, is poorly understood, mainly due to lack of data.

To help improve this understanding, Lewis and her team created the largest and most geographically comprehensive dataset of antigenic variation. They amassed and characterised antigens from nearly 600 flu viruses dating back from 1930 through to 2013 and collected from multiple continents, including Europe, the US, and Asia. They included nearly 200 viruses that had never been studied before.

Analysis of their data reveals that the amount of antigenic diversity in swine flu viruses resembles the diversity of H1 and H3 viruses seen in humans over the last 40 years, driven by the frequent introduction of human viruses to pigs. In contrast, flu from birds has rarely contributed substantially to the diversity in pigs. However, little is currently known about the antigenic relationship between flu in birds and pigs.

"Since most of the current swine flu viruses are the result of human seasonal flu virus introductions into pigs, we anticipate at least some cross-protective immunity in the human population, which could potentially interfere with a re-introduction of these viruses. For example, the H1N1pdm09 viruses circulating in both humans and pigs are antigenically similar and therefore likely induce some immunity in both hosts," says Lewis.

"However, for the H1 1C, H3 3A, and H3 3B human seasonal lineages in pigs, the risk of re-introduction into the human population increases with the number of people born after the circulation of the human precursor virus, and is increased by the antigenic evolution of these viruses in pigs. Earlier introduced lineages of human H1 and H3 viruses therefore pose the greatest current risk to humans, due to the low or negligible predicted levels of cross-immunity in individuals born since the 1970s."

Swine flu causes symptoms such as coughing, fever, body aches, chills, and fatigue in humans. Pigs can also experience fever and coughing (barking), along with discharge from the nose or eyes, breathing difficulties, eye redness or inflammation, and going off feed - although some display no clinical signs at all.

Vaccination to control flu in pigs is used extensively in the US and occasionally in other regions. Control strategies vary by region, with some countries not using any vaccinations, while others produce herd-specific vaccines for individual producers. There is no formal system for matching vaccine strains with circulating strains, however, and no validated protocols for standardisation and effective vaccine use.

" ̽��ֱ��significant antigenic diversity that we see in our data means it is highly unlikely that one vaccine strain per subtype would be effective on a global scale, or even in a given region," says co-author Colin Russell, also from the ̽��ֱ�� of Cambridge.

"Our findings therefore have important implications for developing flu vaccines for pigs. They also emphasise the need for more focused surveillance in areas with a high pig population density, such as China, and situations where humans and pigs have close contact, in order to better assess the incidence of transmission between the animals and risk of spreading to humans."

Reference:

̽��ֱ��paper ' ̽��ֱ��global antigenic diversity of swine influenza A viruses' can be freely accessed online at http://dx.doi.org/10.7554/eLife.12217.

Originally published as a press release by eLife.

̽��ֱ��wide diversity of flu in pigs across multiple continents, mostly introduced from humans, highlights the significant potential of new swine flu strains emerging, according to a new study.

These flu viruses pose a serious threat to public health because they are no longer similar enough to the current human flu strains for our immune systems to recognise them

Nicola Lewis

Robert Shell

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

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Researchers to explore the role of wild birds in the spread of avian flu viruses

gm349 — Thu, 06 Jun 2013 09:55:04 +0000

A new initiative to study the spread of avian flu by wild bird populations launched today at Ilia State ̽��ֱ�� in Georgia. ̽��ֱ��three-year international collaboration will examine the ecology and evolution of avian influenza viruses in their natural hosts, waterfowl.

Aquatic birds are the natural reservoir for influenza A viruses. However, these viruses can sometimes infect other animals such as pigs and humans, potentially resulting in an epidemic or even a pandemic because the new host species doesn’t have immunity to these avian flu viruses.

This ever-present risk means it is important to understand what flu viruses circulate in wild birds, and what risk these viruses might pose to other animal species. In addition, occasionally when avian flu viruses infect poultry they can mutate into a more deadly form of flu. This highly pathogenic strain of avian flu is not only more deadly in birds than other avian flu viruses but is also more deadly than the common seasonal human flu if it infects people.

Since the emergence and westward spread of the highly pathogenic A/H5N1, one of the unanswered questions is what role wild birds, particularly long-distance migrants, play in the dissemination of influenza A viruses from Southeast Asia to other geographic regions. As Georgia bridges Western Asia and Eastern Europe and is home to wild water birds from many different parts of Eurasia during migration and winter, it is an ideal location to undertake the research.

To find out more about how the viruses spread, the researchers will map circulating avian flu strains in birds in the region as well as studying the movements and population structure of the birds themselves as currently, very little is known about the migratory routes wild birds take to reach breeding and overwintering grounds.

Dr Nicola Lewis, lead researcher on the project from the ̽��ֱ�� of Cambridge, said: “Three migratory flyways converge in the Caucasus region so avian flu viruses that had been infecting birds in one part of Asia might get the opportunity to spread to birds flying in from other regions, and we think that this is most likely to happen in places such as Georgia, where birds from many different parts of Eurasia mix in large numbers during migration and during the winter.

“Knowing where bird populations fly will ultimately allow us to assess what risk might be for an avian flu virus, particularly a deadly one, in one region being taken by a wild bird as it migrates to another region in Asia.”

̽��ֱ��Cambridge researchers will be working with leading Georgian scientists to address these key questions about avian flu viruses in wild water birds.

Lewis added: “By understanding how these avian flu viruses evolve in wild birds and the risk wild birds might pose in spreading infectious diseases, this international scientific collaboration will inform both global animal and public health.”

As well as improving avian influenza virus surveillance in the region, the project will also increase the diagnostic and scientific expertise in Georgia by training local Masters students, academics and laboratory staff to use state-of-the art infectious disease analyses. Integrating Georgia more fully into the international scientific influenza community will provide a much more comprehensive picture of the spread of avian flu.

̽��ֱ��collaboration includes the ̽��ֱ�� of Cambridge, the Animal Health and Veterinary Laboratories (AHVLA) in the UK, Ilia State ̽��ֱ��, the Georgian National Centre for Disease Control and Public Health, the Laboratory of the Ministry of Agriculture of Georgia and the Richard G. Lugar Center for Research in Tbilisi, Georgia.

Scientists focusing on the ecology and evolution of avian flu.

Knowing where bird populations fly will ultimately allow us to assess what risk might be for an avian flu virus, particularly a deadly one, in one region being taken by a wild bird as it migrates to another region in Asia.

Dr Nicola Lewis, lead researcher on the project from the ̽��ֱ�� of Cambridge

Waterfowl

USFWS Pacific Southwest Region from Flickr

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