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Highly Pathogenic
Avian Influenza
A(H5N1)
Vivien G. Dugan, PhD
Director, Influenza Division
National Center for Immunization and Respiratory Diseases
Centers for Disease Control and Prevention
June 27, 2024
•HPAI A(H5N1) detected in birds in 1996
A(
H5N1) is n ot a new threat
•Sporadic HPAI A(H5N1) virus infections of
mammals
have been reported since 2003 -2004
•A(H5N1) clade 2.3.4.4b viruses emerged in wild b
irds in 2020
•29 human cases of HPAI A(H5N1) have been d
etected globally since January 2022
U.K. (5), U.S. (4), Sp ain (2), Vietnam (2), China
(2), Ecuador, Cambodia (11), Chile, AustraliaOverview of HPAI A(H5N1)
Avian Influenza Communication Resources | Bird Flu | CDC2
Human A(H5N1) Cases Since 1997
Technical Report: June 2024 Highly Pathogenic Avian Influenza A(H5N1) Viruses | Bird Flu | CDC3
HPAI A(H5N1) in Dairy Cattle:
Current Situation and Response Updates
4
•USDA has confirmed A(H5N1) virus
in
fections of dairy herds in >100
farms across 12 states
Clade 2.3.4.4b virus
High levels of virus in raw milk
•Other animal species reported in a
ssociation with infected dairy
herds in the United States include:
Wild birds, cats, racoon, opossums
•Wide range of infected wild bi
rds, terrestrial and marine
mammal species worldwideHPAI A(H5N1) in Dairy Herds
Highly Pathogenic Avian Influenza (HPAI) Detections in Livestock ; WAHIS (woah.org)
5
A(H5N1) Human Cases
•April 1 – Texas announced 1st human infection
of HPAI A(H5N1) virus*
•May 22 – Michigan announced 2nd human
infection of influenza A (H5)†
•May 30 –Michigan announced 3rd human
infection of influenza A (H5)†
•Adults working at dairy farms and in contact
with cows
•1st and 2nd cases reported conjunctivitis only,
3rd reported minor respiratory symptoms
•All offered oseltamivir, mild illness and recovered without hospitalization
•No human- to-human transmission
* Health Alert: First Case of Novel Influenza A (H5N1) in Texas, March 2024 | Texas DSHS
† Influenza A (H5N1) (michigan.gov)6
A(H5N1) Human Cases – Virus Sequences to Date
•Diagnostics: No impact to current CDC influenza diagnostic
assay's ability to detect A(H5N1) viruses
•Treatments: No known markers of resistance to FDA
approved antiviral drugs (polymerase acidic inhibitor: baloxavir ;
neuraminidase inhibitors: oseltamivir, peramivir, and zanamivir)
•Candidate Vaccine Viruses (CVVs)
HA of human influenza virus very closely related to two available CVVs
CVVs expected to provide good protection against this virus
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•Since March 2024, d uring the current HPAI A(H5N1) outbreak in dairy cattle, at least 690 people monitored from affected
farms, at least 51 tested, 3 positives (1 in TX, 2 in MI, last case detected May 30, 2024)
•Since March 2024, public health laboratory monitoring includes testing of 30,163 specimens have been tested using a
p
rotocol that would have detected A(H5N1) and other novel virusesSurveillance, Human Monitoring, and Testing
How CDC is monitoring influenza data among people to better understand the current avian influenza A (H5N1) situation | Bird Flu | CDC, Weekly U.S. Influenza Surveillance Report | CDC8
No indicators of unusual influenza activity in
people, including avian influenza A(H5N1)
‘High’ Wastewater Sites and H5 Detections
How CDC is monitoring influenza data among people to better understand
the current avian influenza A (H5N1) situation | Bird Flu | CDCDeveloped Levels for Influenza
A Virus in Wastewater
•Influenza A Virus Level metric
•Compare current level to levels
at the
same site during the
2023- 2024 influenza season
•Flag ≥80th percentile as “high”
•Outreach to state/local part
ners in "high" areas, as
well as notifying state, local, and federal partners
9Data from June 2, 2024 – June,15, 2024
Epidemiologic Investigations
•Health and agricultural partners at local,
state and federal level, and affected farms using One Health approach
•Important public health questions
Evidence of infection in exposed populations?
Spectrum of illness and rate of asymptomatic
infections?
Types of exposure on farms/dairies?
Behaviors associated with human infections or protection from infection?
•Assess risk for symptomatic and
asymptomatic infection and a survey to
assess exposures
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Avian Influenza Communication Resources | Bird Flu | CDC
Summer Influenza Surveillance Priorities
•Continued monitoring of people with recent exposure on confirmed farms
•Facilitate detection of A(H5N1) human cases in the community through
enhanced, national surveillance at seasonal influenza levels
Subtyping of influenza A positive specimens, expanded specimen sources
Continued surveillance of lab- confirmed influenza associated hospitalizations
through FluSurv -NET
•Continued follow -up for areas that flag in syndromic and wastewater data
•Provider outreach to continue influenza testing through summer,
particularly for patients with recent history of relevant exposures
CDC Strategy for Enhanced Summer 2024 Influenza Surveillance | Avian Influenza (Flu) 11
Global Surveillance is Central to Prevention and Mitigation
•Characterize human
and z
oonotic
influenza viruses
•Contribute data for bi
annual vaccine
composition
•Generate and e
valuate Candidate
Vaccine Viruses
•147 WHO National Influenza Centers in 123 Member States (CDC Atlanta Influenza Laboratory is one)
•7 WHO Collaborating Centers for Influenza (CDC is one)
•12 WHO H5 Reference Laboratories
Global Influenza Surveillance and Response System (GISRS) (who.int)12
Public Health Risk
•Overall risk to the public remains low
•Increased risk with exposure to
infected animals or environment
(occupational, recreational)
•Exposed individuals should monitor
for symptoms after first exposure
and for 10 days after last exposure
Highly Pathogenic Avian Influenza A(H5N1) Virus in Animals: Interim Recommendations for
Prevention, Monitoring, and Public Health Investigations | Avian Influenza (Flu) (cdc.gov)
Avian Influenza Communication Resources | Bird Flu | CDC13
CDC’s HPAI A(H5N1)
Response Priorities
•CDC leads public health activities and is
working closely with USDA, FDA, and
state and local public health agencies
•Supporting and engaging public health and agricultural partners using a One
Health approach
•Protecting human health and safety
•Understanding risk to people from A(H5N1) viruses
•Assessing A(H5N1) viruses for genetic
changes
14Avian Influenza Communication Resources | Bird Flu | CDC
Resources from CDC
15•Situation Updates
CDC A(H5N1) Bird Flu Response Update | Avian Influenza (Flu)
•Surveillance Updates
How CDC is monitoring influenza data among people to better
understand the current avian influenza A (H5N1) situation | Avian
Influenza (Flu)
•Technical Report
Technical Report: Highly Pathogenic Avian Influenza A(H5N1) Viruses | Avian Influenza (Flu) (cdc.gov)
•Updated Recommendations
Highly Pathogenic Avian Influenza A(H5N1) Virus in Animals: Interim
Recommendations for Prevention, Monitoring, and Public Health Investigations | Bird Flu | CDC
Recommendations for Worker Protection and Use of Personal
Protective Equipment (PPE) to Reduce Exposure to Novel Influenza A Viruses Associated with Severe Disease in Humans
•CDC Public Health Science Agenda
CDC Public Health Science Agenda for Highly Pathogenic Avian
Influenza A(H5N1) – June 2024 | Bird Flu | CDC
CDC A(H5N1) Bird Flu Response Update June 21, 2024 | Bird Flu | CDC
Questions