Monday, 6 May 2013

H7N9 Weekly wrap-up. Bird flu, what bird flu?

We finished Week 5 with astonishingly few new notifications and a lot more difficulty finding key dates for hospitalization, death and discharge. For example, a 55-year old male named Jiao from Hunan province has been variously cited as being the 25th or 27th death associated with H7N9. No-one seems to have a name for the 26th death. Just 1 disease onset and 2 deaths deaths during that period (see the many charts on the H7N9 page) making it the least fatal week of the outbreak. A total of 26 cases have been discharged from hospital (see Case chart on H7N9page, with perhaps another 9 unnamed discharges from Zhejiang. No new cases reported from Shanghai, Beijing, Anhui, Jiangsu, Henan or Shandong. Lab confirmations for cases with dates of onset preceding Week 5 appeared for Jiangxi, Fujian, Hunan and Zhejiang. 

Considering how steep the rate of confirmations was for Zhejiang in particular, the drop off is quite remarkable. The wet market closures seem to be the most popular factor in the decline of new (severe) human cases but there is still no word on prospective PCR screening for H7N9 among non-severe cases or among those without chronic underlying conditions.

So, as far as we know, pneumonia remains the most frequent indicator of H7N9 infection and that seem to be among mostly males with a constellation of underlying disease and infection. 

Week 5 saw a flurry of peer-reviewed scientific papers emerge. Some better-defined the clinical cases, other reported risks based on what we know from past influenzaviruses and others described the avian and genetic pathways for the parent and grandparent H7 and N9-containing viruses that seem to lead to the creation of H7N9. Intriguingly, there are still very few reports of H7N9 in the ducks, chickens and wild birds proposed as the hosts from which humans catch the virus.

While markets have been found to contain H7N9-positive birds, there are remarkably few human cases among market vendors or those working with the feather plucking machines (another proposed transmission route proposed during Week 5). Could vendors have pre-existing immunity? 

So another curious week with plenty of questions raised, but cases and deaths declining.