OmniVira

Detection of Divergent Highly Pathogenic Avian Influenza A(H5N1) Clade 2.3.4.4b Virus, São Paulo, Brazil, 2025.

Jansen de Araujo Luciano M Thomazelli Thomas P Fabrizio Gustavo O Fenner Erick G Dorlass Ana K A Eisen Viviane F Botosso Marcello S Nardi Caroline C Aires Sergio M N Teixeira Roberta M de Azevedo Mayra H Frediani Tatiana Ometto Mário G L Barboza Edmarcia E de Souza Carsten Wrenger Richard J Webby Edison L Durigon
PMID42811438 DOI10.3201/eid3210.260723 Year2026 Journal Emerging infectious diseases Emerg Infect Dis Languageeng Publication statusActive
Active Last checked 2026-10-01 03:31:09 Source: NCBI PubMed

Abstract

In 2025, we detected highly pathogenic avian influenza H5N1 virus in dead waterfowl at Ibirapuera Park, São Paulo, Brazil. Genomic characterization indicated a reassortant virus that emerged from locally circulating low pathogenicity avian influenza viruses and highly pathogenic North American lineages. Our results highlight cross-species transmission risk and underscore the need for enhanced surveillance.

Supporting text Virus Host Location
Brazil 52 genomic surveillance 12 H5N1 88 highly pathogenic avian influenza 17 Influenza 63 viral 2 viruses 120 Influenza A Virus, H5N1 Subtype 308 Influenza in Birds 352 Animals 1981 Birds 215 Brazil 52 Genome, Viral 324 Phylogeny 826 Reassortant Viruses 109

Evidence records

2 total
Zoonotic Surveillance
1 records · 1 evidence types
Evidence type Viral Detection
1 records
OVE12257 Viral Detection
Key finding

Highly pathogenic avian influenza H5N1 virus was detected in dead waterfowl at Ibirapuera Park, São Paulo, Brazil, in 2025.

Virus
Influenza A virus H5N1
Host
dead waterfowl Natural host
Location
Brazil
Supporting text

In 2025, we detected highly pathogenic avian influenza H5N1 virus in dead waterfowl at Ibirapuera Park, São Paulo, Brazil.

Method
genomic characterization
Geographic raw
Ibirapuera Park, São Paulo, Brazil
Country inferred
BRA
Genomic Evolution
1 records · 1 evidence types
Evidence type Recombination or Reassortment
1 records
OVE12258 Recombination or Reassortment
Key finding

The detected H5N1 virus in São Paulo was a reassortant derived from locally circulating LPAI viruses and highly pathogenic North American lineages.

Virus
Influenza A virus highly pathogenic North American lineages Influenza A virus H5N1 reassortant virus
Host
Not specified
Location
Not specified
Supporting text

Genomic characterization indicated a reassortant virus that emerged from locally circulating low pathogenicity avian influenza viruses and highly pathogenic North American lineages.

Event type
reassortment