H7N9 snapdate: hotspot map

Click on image to enlarge.
Modified from here.  

Guangdong province starts to see red while Guangxi very quickly moved from 1 case to 3.

Activity in China's north east remains low.

H7N9 snapdate: cases in 2013 vs 2014...[UPDATED]

Since I started tracking this beastie (the same time I started this blog) in April 2013, I've tended to use weekly data - because more is more!

This one presents the data by month and it really highlights that - at least to date - human infections with H7N9 have been focused on a single month. 

That's not really a seasonal thing (although it is a colder month) - just opportunistic - to my mind anyway. An opportunity last year that seemed to have been lost to H7N9 by market closures, cessation of the movement of its host and the encroaching warmer weather. 

With markets now closed in Zhejiang and Shanghai, we should see some impact taking effect once a 2-week period has passed, which is 2-weeks from the 24-Jan. 

Click on image to enlarge.
Plotted by week of disease onset or date
reported if onset data unavailable. Keep in
mind that, on average (n=199/273 data points)
there are around 9-days between illness
onset and case announcement.

Today signals the end of the 1st week; 7-Feb the second week. At the very least, Zhejiang-acquired cases should wither by the end of that period & hopefully an effect will be visible leading up to it. It may still take another week to 10-days to see that trickle through the reporting system (see figure legend). Last night we saw 4 new cases announced from Zhejiang province. Fewer than some weeks, more than others.

So Zhejiang is our sentinel for an impact from market closures. The place to keep an eye on in the coming weeks as an indicator of H7N9 activity in the region. Or it might just all be down to warmer weather shooing the H7N9 away! But at least we have last year as a guide of what to expect this year. If you can expect anything from influenza.

And just to add, there are also cases acquired in areas with active markets and those acquired at rural farms etc during the mega-travel period that is the Chinese spring festival....weeell, let's  just observe and see how those chickens fall as they do.

H7N9: Zhejiang in 50 cases...

Click on image to enlarge.

A quick look at the same number of cases (50) during the same period of time (2-months) in Zhejiang province, across 2-years. In 2014, between 23-Nov to 23-Jan, H7N9 case numbers surpassed 50 whereas in 2013 H7N9 cases did not reach 50 during the 1st wave.

Back on the 23-Jan it did not look like it would make it. Things move fast in influenza-town and prediction is a mug's game.

All a bit arbitrary, yet it is another indicator in addition to starting earlier and from more provinces than in March 2013, that H7N9 case numbers will be higher in 2014 than we saw last year and may well tear through the human case tally for that other "bird flu", H5N1.

As @influenza_bio noted on twitter this evening, there have been a lot of farmers listed in the FluTrackers case list of late.

A quick tabulation shows that 9.5% of FT cases between #1 & #137 have "farmer" in their description while none do between #139 & #177. However, 33.3% of the cases between #178 & #274 are described as farmers. What type of farmer, and how thoroughly this description was initially reported in the provincial media release is completely unknown so take this paragraph with a big grain of chicken salt.

There have been 6 new H7N9 cases added tonight, so far including 2 deaths, one among the new list and 1 of a previously reported case.

Zhejiang: more live bird market closures...

FluTrackers have posted a report originating from the Ningbo evening news in China stating that more markets in Zhejiang province, in the regions below, have been closed for cleaning and disinfection in an attempt to bring the Province's H7N9 outbreak under control...

These regions have already suspended trading...

• Hangzhou city (which I noted here)
• Xiaoshan District
• Yuhang District
• Jinhua
• Shaoxing City

This new report notes closure of the following markets in the "main city of Ningbo" from 26-Jan..

• Haishu District
• Jiangdong District
• Jiangbei District
• Yinzhou District

Exotic bird imports and pigeon flying has been banned.

Influenza A(H7N9) virus case appears in Zhejiang province....

Look I know hypotheses are there to be disproved  but did this one have to be shot down in flames 60-minutes after I said at a talk today, "...perhaps the very quick and large scale bird cullings and the live bird market closures actually eliminated the particular H7N9 that was spreading through humans in South East China earlier in the year. Perhaps even  reaching far enough back to require a whole new random chance mixture of the different H7s and N9s and other genome segments to occur before that virus would ever be seen again."

Brrraaappppp!!!!!

Today we see the first new H7N9 case since early August (which was an onset of July 28th).

A 35-year old male from Shaoxing County, hospitalised on October 8th, tested positive by PCR. He is in serious condition.

Peak daily temperatures are not high in this part of the world currently - below 25'C for the week.

It looks like H7N9 might be well entrenched after all. Where there are severe cases, there may well be less severe ones. 

A scientific article that I reviewed back in August, written by Yang and colleagues, showed that some poultry workers had been exposed to H7N9. These were relatively younger and healthier people than the PCR-positive ill H7N9 cases.

We're in for some interesting times ahead with H7N9; it's not done with us yet.

3 in 50 mostly asymptomatic workers handling live poultry have H7N9 antibodies...

Earlier in the week Yang and colleagues, publishing in the Journal of Infectious Diseases, found that among 1570 people from Zhejiang province tested for antibodies towards influenza A(H7N9) virus, 25 of 396 (6.3%) poultry handlers from live poultry markets had antibodies detected. Only 9 (0.8%; statistically significantly fewer) of the 1129 community members showed signs of an immune response to H7N9 infection while 33 of 45 (73%) laboratory confirmed H7N9 cases had significant levels of antibody.

No poultry handlers (mostly exposed through slaughtering) had H7N9 in nasal swabs collected at the time of blood sampling, probably reflecting that collection had occurred after the infection that elicited antibody had resolved. Less than 4% of poultry handlers or the general community had fever or respiratory symptoms at sampling compared to 100% of the lab-confirmed group.

This partially answers one of my questions from earlier in the year - but leaves the part which asks: if the main H7N9 host is poultry (and not wild birds), why don't we see the majority of ill people coming from the poultry worker population? While aerosol transmission has been described as low among ferrets, H7N9 transmission might be effective enough to explain the other human H7N9 cases not due to slaughtering of poultry.

Now we can say that poultry handlers are getting exposed and 3 in every 50 are getting infected (or mounting an immune response, to be pedantic). Only 3% of this population and 10% of the general community had underlying diseases compared to 64% of the lab confirmed cases. Sex of the groups did not seem to play a role but those aged ≥60-years were over-represented among the lab-confirmed H7N9 cases (53% of them) compared to poultry handlers (1%-a much younger population) or the general community (19%).

As for MERS-CoV, underlying conditions and older age are clearly important risk factors for more severe disease.

The authors also noted that higher antibody levels were found in survivors that in fatalities, perhaps suggesting (a) the fatalities did not have time to mount a suitable response before they succumbed or (b) the antibodies protected against worse outcomes. Poultry workers do not always have serious disease, which probably means lower viral loads and thus reduced likelihood that they are major sources of human-to-human transmission.

In a previous study by Bai et al, using one of same sort of antibody detection techniques (haemagglutination inhibition), no poultry handlers from were found to be positive prior to late 2013. So this new article proves the emergence of H7N9 human infections is a recent event. And this provides Chapter 2 on that earlier post. 

Some questions still remain in my mind:

• Are these 3/50 poultry handlers also getting moderately or severely ill? 
• How often does infection in this group result in asymptomatic or mild disease?
• If disease is mild or asymptomatic in poultry handlers, is it because these workers are exposed to poultry with other influenza viruses comprised of proteins that are or are sufficiently related to H7 and so they already have some protective immunity to moderate their disease after H7N9 infection?