Bird flu may not have become the threat to humans that some predicted because our noses are too cold for the virus to thrive, say UK researchers.
I had not realized that there was such a difference between the temperature in our nose and our bodies. Apparently the low temperatures in the nose are very important as a first line of defense against a range of invaders, both bacterial and viral. It made me wonder if things that increase nasal temperatures, like allergies, might also have some impact on the spread of flu.
I would expect that the oral temperature (about 37 °C) is much closer to our core temperature since that is where we used to place thermometers. ANother reason not to breathe through your mouth.
Of course, the BBC does not link directly to the paper itself but here it is: Avian Influenza Virus Glycoproteins Restrict Virus Replication and Spread through Human Airway Epithelium at Temperatures of the Proximal Airways. It is Open Access so anyone can read it.
So avian-derived influenza viruses have a hard time replicating because of the temperatures in our nose. Now, all this work was done in a model and not inside someone’s nose but it is very interesting nonetheless.
The authors examined what sorts of amino acid changes were necessary to alter the temperature sensitivity in the virus, so that it could replicate at nasal temperatures. All to give insight into what to look for in the wild, like during a pandemic, where antigenic drift as the virus accumulates amino acid changes, can represent increasing adaptation to human beings.
As I have mentioned before (and also here), the initial outbreak of the 1918 flu pandemic was relatively mild but 5 months later it came back with a vengeance. In that five month period, it became more and more adapted to a human host than to a bird.
It appears from this work that anything that increases the temperature of the nasal passages might make it easier to spread the flu.
I wonder if people with hay fever, or other allergies that raise the temperature of the nose, are at greater risk to get the flu? One of the major things that histamine release does is raise the temperature of the nasal passages.
It might explain some of these late season flu outbreaks as seasonal allergies from pollen cause a rise in the nasal temperatures. Plus, their noses often plug up due to the allergy, requiring them to breathe through their mouths, which has a temperature more favorable to viral replication.I ‘ve tried to find something in the literature about this and failed. If anyone has a link to some published work on this, please let me know.
Combating the increase in temperature in the nose is exploited in the hunt for new anti-histamines. (As an aside, compare how we examine these sorts of questions regarding vascular changes in the nose with what was done in the 40s. Stick a balloon up my nose? No thanks. I love new technology.) So, one might expect to see a drop in flu cases in areas where lots of people use anti-histamines. Any epidemiology out there on this?
Anyway, I think I’m going to patent a ‘nose cooler’ device. Keep it cool and stop the flu. STarve a cold and freeze the flu. Something like that.
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