# 2019
What little media attention we've seen surrounding pandemic flu over the past few years has been largely focused on the H5N1 bird flu virus. Scientists know, however, that there are other influenza's out there in the running to spark the next pandemic.
The H7 virus, while a dark horse candidate, has already made a small number of campaign appearances.
The following is a list of known of human H7 infections since 2002 (stats borrowed from CIDRAP's Summary of Avian Influenza Cases in Humans)
- 2002 H7N2 1 case United States (Virginia) Evidence of infection was found in one person in Virginia following a poultry outbreak
- 2003 H7N7 89 cases (1 death) The Netherlands During an outbreak of H7N7 avian influenza in poultry, infection spread to poultry workers and their families in the area (see References: Fouchier 2004, Koopmans 2004, Stegeman 2004). Most patients had conjunctivitis and several complained of influenza-like illness. The death occurred in a 57-year-old veterinarian. Subsequent serologic testing demonstrated that additional case-patients had asymptomatic infection.
- 2003 H7N2 1 New York The source of exposure was not determined
- 2004 H7N3 2 cases Canada (British Columbia) Two poultry workers became ill during an outbreak of H7N3 avian influenza in poultry (see References: Health Canada 2004). Both had conjunctivitis.
- And 4 people were confirmed to have contracted H7N2 in the UK last year.
Today, according to AFP, a study has been released in PNAS (Proceedings of the National Academy of Sciences) suggesting that the RBD (receptor binding domain) of the H7N2 virus may be evolving to more easily infect humans.
RBD's are the area of a virus that allows it to attach to receptor cells in a host's body. Different viruses are attracted to different types of cells, which explains why some viruses that affect man, don't affect other species, or vice versa.
Receptor cells have strands of sugar (carbohydrate) molecules on their surface. These carbohydrate molecules - called glycans' - form a dense sugary coating to all animal cell membranes.
When a virus meets a compatible receptor cell, they bind. And infection ensues.
For more detailed background on receptor binding domains you can read posts here and here.
The referenced study does not yet appear to be online at PNAS, so detailed comment will have to wait until I can read it.
A hat tip to Dutchy on Flutrackers for finding this article. I will try to follow up on this in the next few days.
Evolution of flu strains points to higher risk
(AFP)
26 May 2008
CHICAGO - Some strains of bird flu are coming ever closer to developing the traits they need to cause a human pandemic, a study released Monday said.
Researchers who analysed samples of recent avian flu viruses found that a few H7 strains of the virus that have caused minor, untransmissible infections in people in North America between 2002 and 2004 have increased their affinity for the sugars found on human tracheal cells.
Subsequent tests in ferrets suggested that these viral strains were not readily transmissible.
But one strain of the H7N2 virus, a low pathogenic avian flu strain isolated from a man in New York in 2003, replicated in the ferret's respiratory tract and was passed between infected and uninfected ferrets suggesting it could be transmissible in humans.
The investigators said the evidence suggests that the virus could be evolving toward the same strong sugar-binding properties of the three worldwide viral pandemics in 1918, 1957 and 1968.
