WHO Avian Flu Risk Assessment - June 2017

WHO H7N9 Epi Curve - June 12th

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Just 12 months ago H7N9 was closing out its 4th, and least impressive, epidemic wave in its short tenure in China.  After making a big splash over 2013-2014, the virus appeared on the decline (see epi curve above), despite dozens of genotypes in circulation.

But the only real constant with influenza is that it is constantly changing.

And so we find ourselves a year later watching the biggest bird flu human epidemic on record winding down, two distinct new H7N9 variants (1 LPAI, 1 HPAI) taking hold, and the virus edging closer to escaping the confines of Mainland China.

The recent surge, and continuing evolution H7N9 in China, has scientists increasingly  concerned.  A few recent blogs include:

PLoS Pathogens: Three Mutations Switch H7N9 To Human-type Receptor Specificity

EID Journal: 2 Expedited HPAI H7N9 Studies

Eurosurveillance: Preliminary Epidemiology & Analysis Of Jiangsu's 5th H7N9 Wave

The saving grace to all of this, so far at least, is that the H7N9 virus still doesn't transmit efficiently between humans. Clusters remain rare, and very few human-to-human transmissions have been observed.

Roughly once a month the World Health Organization releases an updated Influenza at the human-animal interface report that details novel human flu infections reported since the last update and provides a risk assessment.

Today's report - covering the 30 days between May 17th and June 15th - adds 47 H7N9 cases. No other avian or novel flu infections were reported during this time period.

Some excerpts from the 5-page PDF report follow, after which I'll return with a bit more.

Influenza at the human-animal interface
 
Summary and assessment, 17 May 2017 to 15 June 2017

• New infections1: Since the previous update, new human infections with influenza A(H7N9) viruses were reported.
•  Risk assessment: The overall public health risk from currently known influenza viruses at the human-animal interface has not changed, and the likelihood of sustained human-to-human transmission of these viruses remains low. Further human infections with viruses of animal origin are expected.
• IHR compliance: All human infections caused by a new influenza subtype are required to be reported under the International Health Regulations (IHR, 2005).2 This includes any animal and non-circulating seasonal influenza viruses. Information from these notifications is critical to inform risk assessments for influenza at the human-animal interface.

(SNIP)

Avian influenza A(H7N9) viruses
 
Current situation: During this reporting period, 47 laboratory-confirmed human cases of influenza A(H7N9) virus infection were reported to WHO from China. Among these cases, one cluster of cases were reported; both cases in the cluster had exposure to live poultry. Cases were reported from Shaanxi province for the first time and cases had likely exposure in Inner Mongolia for the first time as well.

1 For epidemiological and virological features of human infections with animal influenza viruses not reported in this assessment, see the yearly report on human cases of influenza at the human-animal interface published in the Weekly Epidemiological Record. Available at: www.who.int/wer/en/
2 World Health Organization. Case definitions for the four diseases requiring notification in all
circumstances under the International Health Regulations (2005). Available at: www.who.int/ihr/Case_Definitions.pdf 3 WHO Cumulative number of confirmed human cases of avian influenza A(H5N1) reported to WHO tables. Available at: www.who.int/influenza/human_animal_interface/H5N1_cumulative_table_archives/en/

Case and cluster details are presented in the table in the Annex of this document. For additional details on these cases, public health interventions, and the highly pathogenic avian influenza (HPAI) A(H7N9) viruses, see the Disease Outbreak News.

As of 15 June 2017, a total of 1533 laboratory-confirmed cases of human infection with avian influenza A(H7N9) viruses, including at least 592 deaths4, have been reported to WHO (Figure 1). The number of human infections with avian influenza A(H7N9) viruses and the geographical distribution of human cases in the fifth epidemic wave (i.e. onset since 1 October 2016) is greater than in any earlier wave.

This suggests that the virus is spreading, and emphasizes that further intensive surveillance and control measures in both the human and animal health sectors are crucial. However, the number of reported confirmed cases has continued to decline over the past few weeks indicating that the peak of cases this wave was reached in mid-February 2017.

According to reports received by the Food and Agriculture Organization (FAO) on surveillance activities for avian influenza A(H7N9) viruses in China, positives among virological samples continue to be detected in poultry from live bird markets, commercial and backyard farms. The agricultural authorities in China have also announced plans to commence vaccination of domestic poultry in certain areas against infection with avian influenza A(H7) viruses beginning in July.5

(Continue . . . .)

 
Although eerily quiet now, just a year or two ago the  WHO considered H5 viruses the most obvious pandemic threat, particularly after Egypt's record setting H5N1 outbreak in the spring of 2015 and the emergence and global spread of H5N8, the reports of a new virus - H5N6 - infecting people and poultry in China. 

Like H7N9, those viruses continue to spread and evolve, and while reported human infections have been few and far between over the past year, they could easily stage a comeback just as H7N9 has over the past 8 months. 

H7N9 is viewed, rightfully so, as having the greatest pandemic potential right now (see Updated CDC Assessment On Avian H7N9 and NPR: A Pessimistic Guan Yi On H7N9's Evolution).

But influenza posesses remarkable evolutionary speed - where generations are measured in minutes or hours, not years or decades - and abrupt changes can occur literally overnight via viral reassortment.

Which means that we could just as easily be blindsided by a different mutated bird flu subtype, one of the many H1, H2, or H3 swine flu viruses in ciruculation around the globe, or something else that isn't even on our radar right now.

Despite the strides that have been made in the identification and understanding of novel flu viruses, less than a month ago in World Bank: World Ill-Prepared For A Pandemic, that organization warned that far too many nations have let pandemic preparedness slide, and that the world remains ill-prepared to face even a moderately severe pandemic.