#19,245
In their latest Influenza at the human-animal interface Summary and risk assessment (from 13 June to 7 July 2026) - published over the weekend - the WHO has announced a 3rd H5N1 case in a Bangladeshi child in the past 6 months.
- Last April, we saw a fatal case reported from the Chattogram Division, in a child who fell ill on January 22nd, was hospitalized on January 28th, and who died on February 1st. The H5N1 infection was only determined posthumously, via lab analysis on Feb 7th.
- In early June we learned of a 2nd case, a child from Sylhet Division who was hospitalized on March 28th with a clinical diagnosis of measles with bronchopneumonia. The child was discharged on March 31st, but delayed testing by the IEDCR only revealed a positive H5N1 result on April 20th.
Today, we have another report which - once again - was only fully diagnosed belatedly, and this time the child was only seen as an outpatient. As with the last case, this case also hails from Sylhet Division.
Avian influenza viruses in humans
A(H5), Bangladesh
On 15 June 2026, Bangladesh notified WHO of one laboratory-confirmed human case of avian influenza A(H5) infection in Bangladesh in a child from Sylhet Division. The case was detected notified through the National Influenza Surveillance, Bangladesh (NISB) platform as an influenza like-illness (ILI) case.
The patient developed respiratory symptoms on 17 May 2026, received outpatient healthcare on 20 May. A clinical sample was collected that day and was received by the Institute of Epidemiology, Disease Control and Research (IEDCR) on 4 June as part of routine surveillance.
The sample tested positive for influenza A(H5) virus by real-time reverse transcription polymerase chain reaction (RT-PCR) on 11 June. The patient is now in good health and reported no travel history and no history of exposure to poultry.
However, poultry deaths were reported in the area surrounding the patient’s residence. The outbreak investigation team identified and followed close and possible contacts. Samples from some of the close contacts as well as animal and environmental samples were collected for testing for influenza. All contacts remained asymptomatic and all samples tested negative for influenza.
This is the third laboratory-confirmed human case of avian influenza A(H5) reported in Bangladesh in 2026, and the 15th human case of avian influenza A(H5) reported to WHO from Bangladesh since 2008, including two fatal cases, one reported in 2013 and one in 2026
Sadly, this is a pattern we see far too often, and not just in Bangladesh. Delayed diagnosis not only endangers the patient's health, it risks unknowingly exposing others to the virus, and delays greatly reduce the effectiveness contact tracing or testing of others who may have been exposed.
We've seen numerous examples (see here, here, here, and here) of delayed diagnosis of novel flu in hospitalized patients, even here in the United States and in Europe (see H9N2 in Italy).
Admittedly, novel flu can often present with atypical signs and symptoms, or may be mild or even asymptomatic, and not justify hospitalization or comprehensive testing (which may not even be available in some parts of the world).
Additionally, standard throat swabs sometimes don't yield a positive result, and viral shedding can fluctuate over the course of infection, making false negatives not uncommon.
Recognizing the problem, in 2024 the ECDC issued guidance for member nations on Enhanced Influenza Surveillance to Detect Avian Influenza Virus Infections in the EU/EEA During the Inter-Seasonal Period.
Sentinel surveillance systems are important for the monitoring of respiratory viruses in the EU/EEA, but these systems are not designed and are not sufficiently sensitive to identify a newly emerging virus such as avian influenza in the general population early enough for the purpose of implementing control measures in a timely way.
In January 2025 we saw a CDC HAN: Accelerated Subtyping of Influenza A in Hospitalized Patients, which urged immediate, and more thorough subtype testing of suspected flu cases.
Since these are recommendations, and not mandates, it isn't clear how fine a net we are casting at the local level (see Idaho Health HAN: Consider Avian Influenza A (H5N1) in Patients with Dairy Cattle or Poultry Exposure).
Today's WHO report also summarizes 2 recent H9N2 cases (see chart below), and a novel H3N2v case from Brazil.
On 25 June 2026, Brazil notified PAHO/WHO of a laboratory-confirmed human infection with an influenza A(H3N2)v virus detected in a child in Santa Catarina state. The patient had symptom onset on 12 June 2026 and due to worsening respiratory symptoms, healthcare was sought on 16 June.
The patient was referred for hospital admission with a diagnosis of Severe Acute Respiratory Infection (SARI). Upon admission, an antigen test confirmed influenza A and the patient was placed in a private respiratory isolation room and antiviral treatment was initiated.
The patient was discharged on 19 June.
A nasopharyngeal swab sample was collected on 16 June and sent to the State public health laboratory for real-time RT-PCR. On 18 June, a swine-origin influenza H3 variant was suspected, and the sample was sent to the Laboratory of Respiratory Viruses, Exanthems, Enteroviruses, and Viral Emergencies (LVRE) at the Oswaldo Cruz Institute (Fiocruz/Rio de Janeiro) on 19 June.
Analyses confirmed the presence of an influenza A(H3N2)v virus via molecular testing and genomic sequencing. An investigation by the state and municipality epidemiological surveillance team found that all contacts were asymptomatic before, during and after the child’s illness.
The child's grandfather worked at a swine nursery housing approximately 5,000 animals, though he noted that sanitary barriers were in place. The child frequently visited the grandfather's home and had contact with him several days a week. This is the first human A(H3N2)v infection detected in the Brazil in 2026 and the first case reportedi n the state of Santa Catarina.
While there is no evidence that HPAI H5 is spreading efficiently from human-to-human right now, the evidence suggests that it is spilling over into humans more often than we know.
And even if there is some (as yet, unknown) species barrier that prevents H5 from ever becoming a pandemic, there are plenty of other viruses out there following similar paths.
Eventually, one of them will get lucky. It's only a matter of time.
