Friday, 19 April 2013

A mutation musing

A collaborative report (by Dutch and Chinese contributor) published yesterday from Eurosurveillance shows that 5/7 H7N9 strains from humans, birds and the environment have an amino acid change in the HA gene called Q226L (the normal" glutamine [Q] found at amino acid position 226 has "mutated" to a Leucine[L]). 

In the past, this change has been associated with binding of influenzavirus to a receptor molecule called alpha(2,6,)-linked sialic acid, which is found in the human upper respiratory tract. 

A virus that is happy to replicate in the upper airways, one of the first ports of call for inspired virus-laded droplets, is going to have a good ability to spread by the aerosol route. [I include the eyes in here - but they may considered anatomically separate and the true first point of contact with virus-laden aerosols as they are probably open more than the mouth. 

Other influenza viruses have been shown, by testing of eye swabs, to cause conjunctivitis at this site and common cold viruses can enter the airways through the tear duct. 

More info on Q226L can be found here and here