Wednesday, May 24, 2017

WHO Avian Flu Risk Assessment - May 2017

H7N9 Epi Curve May 16th, 2017 - Credit WHO


A glance at the chart above shows that Mainland China's 5th H7N9 epidemic wave continues to break all records - and if the expected summer lull doesn't kick in soon - could conceivably equal the combined total of the first four waves before it ends in in late September.
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 25 days between April 22nd-May 16th - adds 93 H7N9 cases, 1 H5N1 case in Egypt,  1 H9N2 case in China, and an H3N2v case in Texas. 

Some excerpts from the 8-page PDF report follow, after which I'll return with a bit more.

Influenza at the human-animal interface

Summary and assessment, 21 April to 16 May 2017

  • New infections1: Since the previous update, new human infections with influenza A(H5N1), A(H7N9), A(H9N2) and A(H3N2) variant 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.
Avian Influenza Viruses

Avian influenza A(H5) viruses

Current situation:
Since the last update, one new laboratory-confirmed human cases of influenza A(H5N1) virus infection was reported to WHO. A 35-year-old male resident of Cairo, Egypt, had onset of illness on 8 April 2017. He was initially treated as an outpatient (while traveling to Saudi Arabia) but was hospitalized on 16 April and treated with antivirals. A sample collected on 17 April tested positive for influenza A(H5N1). The patient recovered and was discharged on 23 April. A week prior to his illness, the case had visited a live poultry market in Egypt where he was in contact with poultry excreta. Follow-up of contacts of the case took place with no further cases reported. Avian influenza A(H5N1) viruses are enzootic in poultry in Egypt.
Since 2003, a total of 859 laboratory-confirmed cases of human infection with avian influenza A(H5N1) virus, including 453 deaths, have been reported to WHO from 16 countries (see Figure 1).
Avian influenza A(H7N9) viruses
Current situation:
During this reporting period, 93 laboratory-confirmed human cases of influenza A(H7N9) virus infection were reported to WHO from China. Among these cases, two clusters of cases were reported. Cases were reported from Shaanxi province for the first time. 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 recently detected highly pathogenic avian influenza (HPAI) A(H7N9) viruses, see the Disease Outbreak News.

As of 16 May 2017, a total of 1486 laboratory-confirmed cases of human infection with avian influenza A(H7N9) viruses, including at least 571 deaths3, have been reported to WHO (Figure 2). 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.
According to reports received by the Food and Agriculture Organization (FAO) on surveillance activities for avian influenza A(H7N9) viruses in China4, positives among virological samples continue to be detected in poultry from live bird markets, commercial and backyard farms.
Risk Assessment:
  1. What is the likelihood that additional human cases of infection with avian influenza A(H7N9) viruses will occur? Most human cases are exposed to the A(H7N9) virus through contact with infected poultry or contaminated environments, including live poultry markets. Since the virus continues to be detected in animals and environments, further human cases can be expected. Additional sporadic human cases of influenza A(H7N9) in other provinces in China that have not yet reported human cases are also expected.
  2.  What is the likelihood of human-to-human transmission of avian influenza A(H7N9) viruses? Even though small clusters of cases have been reported, including those involving healthcare workers, currently available epidemiological and virological evidence suggests that this virus has not acquired the ability of sustained transmission among humans, thus the likelihood is low.
  3. What is the risk of international spread of avian influenza A(H7N9) virus by travellers? Should infected individuals from affected areas travel internationally, their infection may be detected in another country during travel or after arrival. If this were to occur, further community level spread is considered unlikely as this virus has not acquired the ability to transmit easily among humans.
         Avian influenza A(H9N2) viruses
Current situation:
One new laboratory-confirmed human case of A(H9N2) virus infection was reported to WHO from China. A 32-year-old man from Beijing developed mild illness on 28 April 2017 and was not hospitalized. He reported no clear exposure to live poultry prior to illness onset. Avian influenza A(H9N2) viruses are enzootic in poultry in China.
Influenza A(H3N2) variant viruses

On 2 May 2017, the United States (US) IHR National Focal Point (NFP) reported the first case of human infection with an influenza A(H3N2)v virus in 2017 in a child from the state of Texas. The child developed an upper respiratory illness on 23 February 2017 and a sample from the patient was confirmed positive for influenza A(H3N2)v virus in late April. The patient did not require hospitalization and swine contact at an agricultural fair was reported in the week preceding illness onset. Further characterization of the virus is underway.
Since reporting of novel influenza A viruses became nationally notifiable in 2005, 402 human infections with influenza A(H3N2)v viruses, including this latest case, have been reported to the US Centers for Disease Control and Prevention (CDC).5
        (Continue . . . )

On May 12th (see Egypt: FAO Reports An H5N1 Case In Cairo), we received a bare bones report of a 3rd H5N1 case in Egypt this year, which is presumably the one referenced in this report.  
Since then we've seen a few media reports of suspected cases, most recently in Beni Suef,  but nothing officially confirmed.
Initial details on the novel H3N2v case were reported in early May by the CDC (see CDC FluView Reports Novel H3N2v Case From Texas).  
Swine variant influenza viruses (H1N1v, H1N2v, and H3N2v) are only rarely reported, but likely occur more often than we know (see CDC: Interim Guidance for Clinicians on Human Infections with Variant Influenza Viruses).
Even more rarely reported are human infections with avian H9N2 (see FluTrackers Global Cumulative H9N2 Partial Case List 1998-2017), although they too are likely more common than are reported.
While H9N2 is viewed to have some limited pandemic potential, it is notably a major player in the creation (via reassortment) of a number of dangerous avian flu subtypes, including H5N1, H5N6, H7N9, and H5N8.
A few recent blogs on its evolution include:
Sci Rpts:Reassorted H9N2:pH1N1 Virus Transmission After Serial Passage In Swine
Vet. Microb.: Analysis Of Korea Lineage Of Avian H9N2 viruses
Emerg. Microbes: Dynamics Of Transmission Of H5N1 & H9N2 In Live Bird Markets - Bangladesh

While the risk assessments for these  viruses remains unchanged - and none have demonstrated the ability to transmit efficiently from human to human -  it is fair to say that  recent developments - particularly with  evolution and spread of H7N9 -  have raised concerns world wide.

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