An Overview of Human Cases of H7N9 in China, April 9, 2013 (updated map April 11, 2013)

Laidback Al · Apr 9, 2013

An Overview of Human Cases of H7N9 in China, April 9, 2013 [FONT=&quot]
[/FONT]Laidback Al, Senior Moderator, www.FluTrackers.com[FONT=&quot]
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The first official cases of human infections of H7N9 in China were reported on March 31, 2013 (link). Since then there have been a total of 28 cases reported in the media and by official public health agencies. Of these, 9 are reported to have died. Several are reported to have recovered, and many are still being treated. The demographics of these cases are described below, although the sample size is too small to draw any substantive conclusions.

Gender Breakdown

Of the 28 cases, 19 are male and 9 are female. Seven males and two female have died to date.

Age Statistics
The ages for the 28 cases range from 4 to 87 years old. The age distribution is skewed toward the elderly. Only one pediatric case, a 4-year-old boy, has been reported.

Onset and Hospitalization

The Incubation period is uncertain. Individuals seem to seek treatment or are hospitalization between 1 and 13 days after onset, with an average passage of time of 5.6 days. The mode for seeking treatment or hospitalization is 4 days. Based on reported onset dates, it appears that the number of cases is rising.

H7N9 China cases 20130409 onsets frequency.webp

Mortality

Among the 9 cases that died, death occurred between 6 and 25 days after onset. For cases with hospitalization data, death occurred between 4 and 11 days after hospitalization.

Source of Infection

The source of infections is unknown at this time. It is speculated that in some of the cases, poultry or other animals were involved because several individuals were associated with butchering and poultry culling. However, almost all of the recent cases have been identified as retired individuals.

Clusters

No family clusters or other clusters potentially representing human-to-human transmission have been officially reported by China.

Geolocation of Cases

 The 28 cases are spread throughout four provinces of Eastern China in widely dispersed areas. No localized geographic cluster has been reported by the Chinese.

Summary

This is a deadly novel virus. It has a high mortality rate among confirmed cases. The number of cases appears to be rising. Without an identified source of infection and the lack of clear-cut evidence of human-to-human transmission, the potential for this influenza virus to cause a pandemic is unknown at this time.

Acknowledgements and Notes
I would like to thank all of the posters and moderators at FluTrackers.com for their efforts at tracking this novel infectious disease outbreak.

The data and information used here have been derived from numerous publicly available online sources and internet media reports. For some individual cases, specific details are lacking or conflicting information is presented in online reports. However, the information and graphics presented here are based on data which is believed to be reasonably accurate and current through April 9, 2013.

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Laidback Al · Apr 9, 2013

Re: An Overview of Human Cases of H7N9 in China, April 9, 2013

Re: An Overview of Human Cases of H7N9 in China, April 9, 2013

Attached is a map for curiosity -

Farmer · Apr 9, 2013

Re: An Overview of Human Cases of H7N9 in China, April 9, 2013

Re: An Overview of Human Cases of H7N9 in China, April 9, 2013

Thanks Al,

Very helpful.

There appears to be a lot of surface water in eastern China. I wonder how many of those water features are currently active given the demand for surface water?

Shanghai is moving out of the colder season into the warmer rainy season. Rainfall appears to peak (historically) in June. It will be interesting to see how the weather affects flu transmission, if at all.

This is a wet place with relatively high humidity year round. It does not appear to have the dry cold weather that is ideal for flu transmission.

http://www.shanghai.climatemps.com/#en-table

Laidback Al · Apr 10, 2013

Re: An Overview of Human Cases of H7N9 in China, April 9, 2013

Re: An Overview of Human Cases of H7N9 in China, April 9, 2013

Farmer said:
Thanks Al,

Very helpful.

There appears to be a lot of surface water in eastern China. I wonder how many of those water features are currently active given the demand for surface water?

Shanghai is moving out of the colder season into the warmer rainy season. Rainfall appears to peak (historically) in June. It will be interesting to see how the weather affects flu transmission, if at all.

This is a wet place with relatively high humidity year round. It does not appear to have the dry cold weather that is ideal for flu transmission.

http://www.shanghai.climatemps.com/#en-table

The blue water features showing rivers and streams are derived from an old publicly-available GIS layer from 2001. This data layer does not have associated names or variable information on stream order. The purple features are man-made water diversion features such as canals and ditches from a publically-available 2007 data file. There is another publicly-available GIS data layer on seasonal lakes in China from 2007, but I did not included it in the map. None of these data layers have any metadata.

With the growing population in China much of the information in these data layers could be outdated. The location of rivers, streams, ditches, and canals in geographic relation to H7N9 cases should be evaluated with caution.
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Vibrant62 · Apr 10, 2013

Re: An Overview of Human Cases of H7N9 in China, April 9, 2013

Re: An Overview of Human Cases of H7N9 in China, April 9, 2013

A common feature of the elderly is that they suffer from immunosenescence i.e poorly functioning immune systems.

Perhaps a common feature of those infected is a sub-optimal functioning or degree of compromise to the immune system? Those who are younger, fitter and have optimal immune system function may be able to fight off infection - i.e suffer from sub-clinical infections. We really need some seroconversion data, but it will be a few more weeks before traceable antibody levels might be present in contacts of known past cases.

Addendum: I have tried without success to find the study report posted on FT (I think) in the last couple of days which suggested there was likely to be little in the way of cross immunity arising from past seasonal flu or pH1N1 infections in any age groups as H7N9 had little in the way of common epitopes with known human flu's. So the immune system argument is possibly more likely.

Laidback Al · Apr 11, 2013

Re: An Overview of Human Cases of H7N9 in China, April 9, 2013

Re: An Overview of Human Cases of H7N9 in China, April 9, 2013

updated map - April 11, 2013

Note: Zhejiang is misspelled in the table in the graphic.
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Laidback Al · Apr 11, 2013

Re: An Overview of Human Cases of H7N9 in China, April 9, 2013 (updated map April 11, 2013)

The plotted locations represent the most specific city or location for each cases as noted in online reports. For cases where no residence is listed, the location plotted is the first hospital where the individual was treated. This assumes that individual was treated at a hospital near his or her home. One case who died, the cook/chef who was a resident of Zhenjiang but was infected in Shanghai, is plotted in Shanghai.

Map of Cases by Onset Week

As shown in the table insert, the number of cases is continuing to rise.

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NS1 · Apr 12, 2013

Re: An Overview of Human Cases of H7N9 in China, April 9, 2013

Re: An Overview of Human Cases of H7N9 in China, April 9, 2013

Vibrant62 said:
A common feature of the elderly is that they suffer from immunosenescence i.e poorly functioning immune systems.

Perhaps a common feature of those infected is a sub-optimal functioning or degree of compromise to the immune system? Those who are younger, fitter and have optimal immune system function may be able to fight off infection - i.e suffer from sub-clinical infections. We really need some seroconversion data, but it will be a few more weeks before traceable antibody levels might be present in contacts of known past cases.

Addendum: I have tried without success to find the study report posted on FT (I think) in the last couple of days which suggested there was likely to be little in the way of cross immunity arising from past seasonal flu or pH1N1 infections in any age groups as H7N9 had little in the way of common epitopes with known human flu's. So the immune system argument is possibly more likely.

The broad trend of the over-60 age factor and the failure to find a validated reservoir should cause us to consider the relationship that emergent H7N9 has to human H3N2. Gain of sub-segment, pre-adapted mammal genetics is a valuable advantage for H7N9 if these two continue to interchange.

Functionally, very few Ab types in humans at this time will cross-react well with H7N9. Any wisp of an idea that one may rely on pH1N1 or H3N2 exposures for priming immune challenge to this emergence is perfectly faulty thinking.

At the moment, details concerning the genetics of the offending pathogen, including the Novel H7N9 HA Q226I adaptation arising at a critical Receptor Binding Site potentially from human H3N2, are available in the GeneWurx Cross Serotype Homology Analysis (Open-Access, Full-Text version). The genetics comparatives are under comprehensive discussion on the wider thread, entitled "China - H7N9 Human Isolates on Deposit at GISAID".

GeneWurx Cross Serotype Homology Analysis, Open-Access, Full-Text version
China - H7N9 Human Isolates on Deposit at GISAID, Comprehensive Genetics Discussion

Laidback Al · Apr 13, 2013

Re: An Overview of Human Cases of H7N9 in China, April 9, 2013 (updated map April 11, 2013)

Looking for latest maps?

Updated maps at this Flutrackers thread.
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An Overview of Human Cases of H7N9 in China, April 9, 2013 (updated map April 11, 2013)

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