Crossroads of Pathogens: The Evolving Threat of Avian Influenza

Influenza viruses are infamous for their ability to mutate and adapt, making the study of their evolution critical for public health. Some like H5N1 are severe, others as H7N3 are typically present with mild symptoms. The classification of influenza subtypes relies on the hemagglutinin (H) and neuraminidase (N) proteins on the viral surface, with 18 H subtypes and 11 N subtypes combining into diverse influenza strains. While most pose limited risks to humans, certain mutations can significantly alter their behavior.

Case 1: Mutated H5N1 in a Vancouver Teen

Canadian teen, who lives in the Fraser Health Region of British Columbia, first developed symptoms on Nov. 2 and was tested on Nov. 8, with a positive result confirmed on Nov. 9.  It was the first positive case of bird flu detected in a human in Canada. The teenager, hospitalized with a mutated H5N1 strain, was unconscious for over two weeks. The teen has made progress and is expected to recover. Alarmingly, this strain exhibits two mutations—HA: E190D and PB2: E627K—also found in the deadly 1918 Spanish flu virus, which killed 5-10% of the global population. These mutations are concerning:
HA: E190D enhances the virus's ability to bind to human receptors, increasing its transmissibility.
PB2: E627K aids viral replication in mammals, raising its virulence and adaptability.

This H5N1 strain is distinct from the version currently spreading among dairy cattle in the U.S (there have been 55 confirmed cases and 461 herds are currently infected). Instead, it aligns closely with strains circulating in Pacific Northwest wild birds. The teenager’s case is Canada’s first confirmed human H5N1 infection. In 2014, a person in the neighboring province, Alberta, was diagnosed with H5N1, it was also the first bird flu infection of the year and the case was fatal.

Health officials remain puzzled about the source of infection, as the teenager had no known contact with infected poultry. While the individual interacted with various pets, none tested positive for the virus. Sporadic human cases of H5N1 have been reported globally, but sustained human-to-human transmission remains absent.

Meanwhile bird flu virus has been found in a batch of raw milk sold in California Raw Farm LLC of Fresno County, California, recalled quart and half-gallon sizes of its raw milk with the lot ID of 20241109 and a best-by date of November 27. One child in California tested positive for avian flu last week but the initial test showed low levels of viral material and repeat testing four days later was negative for bird flu but positive for other common respiratory viruses. An adult with underlying conditions hospitalized on August 22 in Missouri and tested positive for H5 (1st US case without exposure to sick farm animals) has since recovered.

The global spread of highly pathogenic avian influenza (HPAI) in wild birds and poultry since 2022 has fueled sporadic human infections. Though current strains lack efficient binding to human upper respiratory tract receptors, the risk of further mutations remains. Continued surveillance and preparedness are essential to mitigate potential threats.

The mutations seen in this teenager’s case echo the devastating potential of influenza viruses when they cross species barriers and adapt to human hosts. For context, the 1918 pandemic emerged from a bird flu strain and reshaped global health paradigms. 

Case 2: Avian Influenza H10N3 in Kunming, China

Similarly, a March 2024 report from Kunming, China, detailed the first human case of H10N3 since the COVID-19 pandemic. A 51-year-old male with prior respiratory conditions contracted the virus after exposure to sick poultry. Though his case was severe, no human-to-human transmission occurred, and adaptive site mutations in mammals were noted.

Case 3: Co-Infection with H5N1 and SARS-CoV-2

A 52-year-old woman presented with persistent fever, severe shortness of breath, and low blood pressure. CT scans revealed lung consolidation and bilateral pleural effusion. PCR analysis of bronchoalveolar lavage fluid identified both H5N1 and SARS-CoV-2, though clinical symptoms were dominated by H5N1 pneumonia. Rapid administration of antiviral therapy resulted in excellent recovery.



REFERENCES

https://vancouversun.com/news/bc-update-teen-bird-flu

Mellis AM, Coyle J, Marshall KE, et al. Serologic Evidence of Recent Infection with Highly Pathogenic Avian Influenza A(H5) Virus Among Dairy Workers — Michigan and Colorado, June–August 2024. MMWR Morb Mortal Wkly Rep 2024;73:1004–1009. DOI: http://dx.doi.org/10.15585/mmwr.mm7344a3

CDC Technical Report: June 2024 Highly Pathogenic Avian Influenza A(H5N1) Viruses https://www.cdc.gov/bird-flu/php/technical-report/h5n1-06052024.html

Zhao Z, Luo S, Gao Y, Dai M, Yan J, Yang Y, Li H, Zhang Y, Mao Z. A case report of human infection with avian influenza H10N3 with a complex respiratory disease history. BMC Infect Dis. 2024 Sep 4;24(1):918. doi: 10.1186/s12879-024-09830-y. PMID: 39232670; PMCID: PMC11373451.

Jin K, Dai Z, Shi P, Li Y, Zhu C. Severe pneumonia with co-infection of H5N1 and SARS-CoV-2: a case report. BMC Infect Dis. 2024 Jan 2;24(1):31. doi: 10.1186/s12879-023-08901-w. PMID: 38166668; PMCID: PMC10763204.

https://www.statnews.com/2024/11/13/bird-flu-canada-teenager-infected-different-strain-than-dairy-cattle/

https://www.cnn.com/2024/11/25/health/bird-flu-california-raw-milk/index.html

https://www.cdc.gov/media/releases/2024/p1122-h5n1-bird-flu.html



Comments

Post a Comment

Popular posts from this blog

A New Onset of Ulcerative Colitis post-2nd-breakthrough-COVID-19

Image
A 21-year-old non-smoking Caucasian male with a history of acute pancreatitis but no other medical issues or family history had two doses of the BNT162b2 mRNA COVID-19 vaccine.  Four months after the second dose he had his first episode of COVID-19. Although not hypoxic, he felt pretty unwell for a week, with a severe cough, fever, generalized body ache, headache, and loss of taste. He received the third dose of the vaccine two months after recovering from COVID. Nine months after the third dose, he had the second episode of COVID-19, during which he was mildly unwell for three days, recovered, and did not require any anti-viral medication or antibiotics. One week post the second episode of COVID-19, he developed diarrhea and abdominal pain. It then progressed to bloody diarrhea. Ulcerative colitis was diagnosed based on his clinical symptoms, biopsy changes, and the exclusion of other causes.  There are ten published case reports about the newly diagnosed ulcerative colitis ...
Read more

COVID in May

Image
Concerns about a potential resurgence of COVID-19 are mounting as summer 2024 approaches.  This is driven by several indicators, including social media posts, healthcare data, and wastewater surveillance across different regions. Our study findings corroborate this trend.  While many forecasters anticipate a surge, others expect a gradual increase through the end of May, and then a decline again around early June. Reports from social media suggest emerging clusters of COVID-19 in Texas, several Canadian provinces, the UK, and on cruises in northern regions such as a Norwegian cruise to Alaska.  Data from Alberta's Respiratory virus dashboard   (total weekly laboratory-confirmed COVID-19 cases) and wastewater surveillance in Calgary indicate an uptick in COVID-19 cases starting April 2024. The most recent statistics from Alberta Health reveal a significant increase in hospitalizations due to COVID-19, with 114 individuals currently hospitalized—an incr...
Read more

Chronic SARS-CoV-2 Shedding

Image
Chronic viral shedding, a condition where the virus continues to be released from an individual's body long after the initial infection, has been observed in many infectious diseases, including COVID-19.  In such cases, individuals may remain asymptomatic or experience only mild symptoms while the virus persists. It remains detectable in repeated tests over an extended period and can still infect others even in nasal swab is negative (which happens quite often ). This was evident in our study.    Recent research by Conway et al. (2024) highlights the possibility of chronic SARS-CoV-2 infection, extending over several months and potentially years. Other studies have documented prolonged asymptomatic infections and extended viral shedding in moderate to severe beyond hospital discharge. Analysis of sequencing data on UK samples taken between 2 November 2020 and 15 August 2022 lead to estimates that 0.1–0.5% of infections may become persistent with typically rebounding high ...
Read more