Monday, 29 April 2013

Son of Shandong's 1st H7N9 case positive for H7N9.

No evidence for human-to-human (h2h) transmission though. No evidence against it being the cause either of course. See my comments from the 18th regarding the first reported H7N9 case and family cluster. They still apply. 

Incubation time being surreptitiously the same as the (presumed) incubation period means nothing. Two people completely geographically isolated could have the the same gap between onsets and the second case would obviously not have been infected by the first. 

Even if the sequences of the two viruses are very similar, that does not prove h2h transmission. Chances are that many of the H7N9s will have very similar sequences reflecting that they have originated form the same animal (or human) source at some point.

What does this mean? 

It doesn't mean the sky is falling - contacts, by their very nature share things. In a family you often share (inhale, have land in your eyes etc) aerosolized (virus-laden) droplets as well as common surfaces contaminated by with those aerosols, when you have an acute virus infection. Coughing and sneezing do that. 

But you also share common tasks. 

There is so far no clear evidence of direct Dad to Son (or Son to Dad) transmission here (there is a timing issue that is intriguing)- the father and son may have simply shared the same airspace (I think its pretty safe to say this is transmitted through the air in some form) with an animal host during contact, handling, butchery, cleaning etc. Despite testing of animals to date finding very few have detectable H7N9 infections.