WHO Novel Flu Assessment - September

#12,809



Roughly once a month during the winter and less often during the summer months 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 just over 60 days between July 25th and September 17h -  chronicles a mix of new human infections from avian H5N1, H7N9, and H9N2 along with swine variant H1N2v and H3N2v. 

Of particular note, we have official word of the first Indonesian H5N1 case in more than 2 years, and the tally of H3N2v cases appears to include only a few of the (roughly 40) cases reported from Maryland, most of which were confirmed after the cutoff date of September 27h.

A few excepts from a much larger report.  Follow the link to download and read it in its entirety.

Influenza at the human-animal interface
 
Summary and assessment, 25 July 2017 to 27 September 2017

New infections1: Since the previous update, new human infections with influenza A(H5N1), A(H7N9), A(H9N2), A(H1N2)v and A(H3N2) variant2 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.
 
Risk management: Selection of new candidate vaccine viruses (CVVs) for zoonotic influenza for influenza pandemic preparedness purposes was done during a recent WHO consultation.

IHR compliance: All human infections caused by a new influenza subtype are required to be reported under the International Health Regulations (IHR, 2005).4 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
 
Current situation:

Avian influenza A(H5) viruses


Since the last update on 25 July 2017, one new laboratory-confirmed human case of influenza A(H5N1) virus infection was reported to WHO from Indonesia.

The patient was a child who had illness onset on 1 September 2017. He was hospitalized on 5 September and on 10 September, a sample collected from the patient tested positive for A(H5N1) virus. The patient passed away on 10 September. Prior to illness onset, he reportedly had exposure to poultry at his house. A joint investigation between the human health and animal health sector confirmed A(H5N1) infected birds in the area and samples collected from all human contacts of the patient tested negative for A(H5N1) virus infection.

Since 2003, a total of 860 laboratory-confirmed cases of human infection with avian influenza A(H5N1) virus, including 454 deaths, have been reported to WHO from 16 countries.5 The last human cases of A(H5N1) virus infection reported from Indonesia occurred in 2015.

Avian influenza A(H7N9) viruses
 
During this reporting period, 7 laboratory-confirmed human cases of influenza A(H7N9) virus infection were reported to WHO from China. Case details are presented in the table in the Annex of this document. For additional details on these cases, public health interventions and avian influenza A(H7N9) viruses, see the Disease Outbreak News.

As of 27 September 2017, a total of 1564 laboratory-confirmed cases of human infection with avian influenza A(H7N9) viruses, including at least 612 deaths6, 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) have been greater than in any earlier wave. This suggests that the virus has spread, and emphasizes that further intensive surveillance and control measures in both the human and animal health sectors are crucial. A decrease in cases occurred during the past few months. However, if the incidence of human cases follows the trends seen in previous years, the number of reported human cases may rise over the coming months. Further sporadic cases of human infection with avian influenza A(H7N9) virus are therefore expected in affected and possibly neighbouring areas. 

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 that vaccination of domestic poultry against infection with avian influenza A(H7) viruses has commenced, in addition to the ongoing poultry vaccination program against avian influenza A(H5) viruses.

Avian influenza A(H9N2) viruses
 
Since the last update, one laboratory-confirmed human cases of A(H9N2) virus infection was reported to WHO from China. The patient is a child who had mild illness onset of 18 September, received outpatient care and had no apparent exposure history to live poultry.

Swine Influenza Viruses
 
Current situation:

Influenza A(H1N2)v viruses 

Two human infections with influenza A(H1N2)v viruses were detected in the state of Ohio in the United States (U.S). Both cases occurred in children who reported contact with swine at an agricultural event prior to illness. The cases were not hospitalized and have fully recovered from their illnesses. No human-to-human transmission was identified. Characterization of the viruses from the cases indicates they are similar to A(H1N2) viruses currently circulating in swine in the USA. Given that the viruses reacted poorly with current candidate vaccine viruses, new CVVS for pandemic preparedness have been proposed.7

Since 2005, 11 cases of A(H1N2)v influenza virus infection have been reported to the U.S. Centers for Disease Control and Prevention (CDC).8 Most cases are associated with mild illness and two have been hospitalized.

Influenza A(H3N2)v viruses 

Since 25 July 2017, 19 human infections with influenza A(H3N2)v viruses were detected in the U.S. in several states.9 All cases reported exposure to swine at an agricultural fair before illness onset. Two cases were hospitalized. No human-to-human transmission was identified. Characterization of the viruses from the cases indicates they are similar to A(H3N2) viruses currently circulating in swine in the USA. Given that the viruses reacted poorly with current candidate vaccine viruses, a new CVV for pandemic preparedness has been proposed.10 Since reporting of novel influenza A viruses became nationally notifiable in 2005, 403 human infections with influenza A(H3N2)v viruses have been reported to the U.S. CDC and 31 of these occurred in 2017.6

        (Continue. . . .)


Given the constant evolution and growing diversity of novel influenza viruses WHO regularly updates their assessment on which viruses should be considered for candidate vaccines for pandemic preparedness.

September's recommendations included two new swine A(H1)v candidate vaccine viruses and 1 H3N2v candidate vaccine virus. 

Last March new candidate vaccine viruses for both H5N6 and H7N9 were announced. Since 2004 37 H5 candidate vaccine viruses have been selected, along with 11 H7N9 candidate viruses, 6 H9N2 virus candidates, and another 10 H1 and H3 swine virus candidates.  

It should be noted that not all of these viruses continue to circulate.

While the likelihood of any one of these novel viruses sparking a human pandemic is considered low, as more viruses emerge and begin to circulate, that risk increases.

How much?   No one really knows.  

Hence the continual surveillance and proactive identification and creation of candidate vaccine viruses.