News Scan for Jul 09, 2018

Mapping H5N1 changes in Egypt
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H3N2v pandemic potential

Study of H5N1 avian flu genetic changes in Egypt finds potential hot spots

A new analysis of a decade's worth of highly pathogenic H5N1 avian flu virus genetic sequences collected from poultry and wild birds in Egypt found 39 distinct substitutions with the possible ability to increase the pandemic potential of the virus, with spatial clustering that focused on two governorates—Alexandria and Beheira—that are located in the northwestern Nile Delta.

Egypt is the country with by far the most human H5N1 infections, and aside from commercial poultry farms, about 4 million to 5 million families raise backyard poultry. The study is the first spatial analysis of key genetic substitutions (KS)—changes that alter the host specificity, virulence replication, transmissibility, or drug susceptibility that make the virus a greater threat to humans. The US-based group published its findings Jul 6 in BMC Infectious Diseases.

The team looked at sequences from 925 viral samples from poultry and wild birds collected from 2005 to 2015 that were in the Influenza Virus Sequence Database hosted by the national Center for Biotechnology Information. They geocoded the isolates and mapped them to identify clusters where rates of KS were high.

Of the 39 distinct KS, 17 had not be previously reported in Egypt. Most involved the surface hemagglutinin and neuraminidase proteins, as well as the interior nonstructural 1 protein. The most frequent types were linked to increased viral binding to mammalian cells and virulence. Samples with high KS detection rates clustered in the two northwestern Nile Delta governorates, which appeared to be hot spots.

The team said the report serves as a helpful baseline for distribution and clustering of KS in Egypt, adding that the high detection rates in the cluster areas raise concerns about the possibility of a pandemic strain developing in the region. "Better geographic data and improved genetic surveillance are necessary to properly evaluate and monitor this potential threat to global public health," they wrote.
Jul 6 BMC Infect Dis study

 

Experiments track pandemic potential of recent H3N2v viruses

Lab tests and animal studies to assess the threat from variant H3N2 (H3N2v) viruses isolated from people from 2011 through 2016 found that they grow well in human epithelial airway cells, but vary in their ability to replicate throughout the respiratory tract and transmit among ferrets, researchers from the US Centers for Disease Control and Prevention reported in the July issue of the Journal of Virology.

A large outbreak of H3N2v occurred in 2011 and 2012 in the United States, mostly in children who were exposed to pigs at county fairs. Though cases have declined since then, scientists continue to monitor the threat. So far this summer, one H3N2v case has been reported, involving an Indiana resident who was exposed to pigs at a county fair.

The researchers in today's study said that, because of the continuous evolution and cocirculation of diverse H3N2 viruses in US swine, it's challenging to predict which ones may transmit to humans. To help understand the pandemic potential of the viruses, the team examined H3N2v replication in cell and animals studies and tested how well the four different samples transmitted through the airborne route in ferrets.

All four viruses showed similar or enhanced replication in human bronchial cells. In experimentally infected mice, the H3N2v viruses were mildly virulent and replicated with different degrees of efficiency. Ferrets infected with the virus had moderate disease with comparable upper airway involvement, but only two of the four viruses replicated in the lower respiratory tract.

In co-housed ferrets, transmission was efficient, but recently isolated H3N2v varied considerably in their ability to spread by respiratory droplets.

The team concluded that efficient droplet transmission shown by some of the viruses, combined with low population immunity against the virus in young children and older adults, underscores the pandemic potential of H3N2v. "Extensive surveillance and risk assessment of H3N2v viruses should continue to be an essential component of our pandemic preparedness strategy," they wrote.
Jul J Virol abstract
Jul 2 CIDRAP News scan on most recent H3N2v case

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