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Highly Pathogenic Avian Influenza A(H5N1) Virus Infection in a Dairy Farm Worker
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- The authors of this article reported a case of highly pathogenic avian influenza (HPAI) A(H5N1) virus in a dairy farm worker in Texas. The worker experienced subconjunctival hemorrhage in both eyes. The results of real-time reverse transcription–polymerase chain reaction testing were presumptive for influenza A and A(H5) virus. The Centers for Disease Control and Prevention subsequently confirmed HPAI A(H5N1) virus infection in the conjunctival and nasopharyngeal swab specimens obtained on the day of symptom onset, with gene segments closely related to viruses detected in dairy cattle and other peridomestic wild birds in Texas.
- These findings suggest human infection in the dairy farm setting and cow-to-human transmission of HPAI A(H5N1) virus. Vigilance is needed because of the potential risk this virus poses to public health.
abstract
This abstract is available on the publisher's site.
Access this abstract nowSporadic human infections with highly pathogenic avian influenza (HPAI) A(H5N1) virus, with a wide spectrum of clinical severity and a cumulative case fatality of more than 50%, have been reported in 23 countries over more than 20 years. HPAI A(H5N1) clade 2.3.4.4b viruses have spread widely among wild birds worldwide since 2020–2021, resulting in outbreaks in poultry and other animals. Recently, HPAI A(H5N1) clade 2.3.4.4b viruses were identified in dairy cows, and in unpasteurized milk samples, in multiple U.S. states. We report a case of HPAI A(H5N1) virus infection in a dairy farm worker in Texas.
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Highly Pathogenic Avian Influenza A(H5N1) Virus Infection in a Dairy Farm Worker
N. Engl. J. Med 2024 May 03;[EPub Ahead of Print], TM Uyeki, S Milton, C Abdul Hamid, C Reinoso Webb, SM Presley, V Shetty, SN Rollo, DL Martinez, S Rai, ER Gonzales, KL Kniss, Y Jang, JC Frederick, JA De La Cruz, J Liddell, H Di, MK Kirby, JR Barnes, CT DavisFrom MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
A brief history of H5N1
Why all the buzz about influenza A(H5N1)? This virus, classified as a highly pathogenic avian influenza or HPAI, has been persistent and worrisome. It first jumped into humans in Hong Kong in 1997; an outbreak that resulted in 18 cases and 6 deaths. Since that time, there have been 887 cases reported worldwide with 462 deaths, resulting in a case-fatality rate of 52%.1 I cut my teeth in national public health response as a participant in a CDC work group formulating surveillance protocols for pandemic influenza in the late 1990s, prompted by the Hong Kong outbreak.
Something, however, happened in 2022. Eurasian-origin HPAI started showing up in Western Hemisphere birds, accompanied by reports of multiple introductions into a wide variety of mammals. The first human HPAI case acquired in this hemisphere was noted in a Colorado poultry worker in 2022 who developed a mild case of influenza characterized by fatigue.2 An earlier 2014 fatality due to H5N1 occurred in Canada; the individual had, however, contracted influenza in China. An Ecuadorian child — exposed to sickened poultry — developed severe pneumonia and sepsis in early 2023,3 followed by a severe case in an adult with pneumonia in Chile. This individual had exposure to seabirds.4
That brings us to Texas in April 2024. A dairy worker exposed to sick cows developed a mild illness with significant conjunctivitis, subconjunctival hemorrhage, and thin serous ocular drainage. Sequencing of viral RNA from a conjunctival swab confirmed influenza A(H5N1) clade 2.3.4.4b. This is the first known mammal-to-human transmission of HPAI. The viral sequences from this case and from dairy cows lack mutations in the hemagglutinin gene that would enhance receptor binding and transmission in humans.
The virological throws of the dice are increasing in frequency, amplified by multiple transmission events in wild and domestic animals. Acquisition of the wrong combinations of receptor-binding mutations and high pathogenicity could lead to a devastating pandemic. Primary care clinicians need to maintain a healthy level of suspicion when encountering atypical presentations of acute respiratory tract infections, particularly when they are out of place, out of time, and out of context.
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