#19,111
Six days ago, in Taiwan CDC: Human Infection with a Novel H7 Avian Virus, we saw the first locally acquired human H7 influenza infection in Taiwan. The following day, that virus was further identified as H7N7.
While this appears to be an isolated incident, cases like this may happen more often than we are aware simply because the index of suspicion is generally low, infections can be mild or moderate, and most testing outside of the hospital doesn't identify the subtype.
It often requires a bit of luck for these cases to be identified. Two years ago 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.
Today, in their first update on this case since last Friday, Taiwan's CDC has released the following (translated) letter to local doctors.
The Centers for Disease Control (CDC) has confirmed its first locally acquired case of H7N7 influenza ADoctors are urged to be vigilant and immediately report and test any suspected cases (CDC Circular No. 605 to the Medical Profession).
Release Date: 2026-04-08Dear medical professionals nationwide,
the Centers for Disease Control (CDC) announced its first locally acquired case of H7N7 influenza A on April 3rd of this year (2023). The case involves a man in his 70s who works in poultry farming and has a history of chronic illness. He developed symptoms of runny nose, cough, and body aches on March 20th and sought medical attention at a hospital on March 22nd due to fever, where he was admitted to the hospital on the same day. Imaging examination revealed pneumonia.
Based on the clinical symptoms and the patient's contact history, the doctor reported the case as a novel influenza A virus and administered antiviral medication. Further testing by the CDC confirmed the patient's sample as H7N7 influenza A virus, a low pathogenic avian influenza virus (LPAI), which remained sensitive to antiviral drugs. The patient's condition improved, and two subsequent tests were negative. He was released from isolation on April 3rd of this year.
To prevent the spread of novel influenza A, physicians are urged to remain vigilant and conduct thorough "TOCC" inquiries during consultations (including travel history, occupation, contact history, and whether there has been any clustering).
If a case simultaneously presents with both "acute respiratory infection, with clinical symptoms possibly including fever (≥38℃), cough, etc." and "clinical, radiological, or pathological findings showing parenchymal lung disease," and has had close contact with a highly probable or confirmed case with symptoms within 10 days prior to symptom onset, has a travel or residence history in areas with novel influenza A outbreaks, or has had exposure to birds or pigs or visited bird or pig-related locations, then the case meets the reporting criteria for novel influenza A.
Reporting and specimen collection should be conducted as soon as possible according to the "Novel Influenza A Reporting Definition and Specimen Collection and Submission Procedures." Guidelines regarding the definition of novel influenza A cases and prevention measures are available on the Centers for Disease Control and Prevention website (http://www.cdc.gov.tw).
Thank you for joining us in protecting the health and safety of the public.
While perfectly reasonable given the current threat level - and the practical limitations of subtype testing in an outpatient clinical setting - this level of surveillance has a fairly low probability of picking up sporadic mild (or even moderate) novel flu cases in the community.
Three years ago, in UK Novel Flu Surveillance: Quantifying TTD, we looked at the UKHSA's Technical Briefing #3, which found that it might take weeks - and hundreds of cases - before community spread of a novel flu could be confirmed using standard surveillance.
In response to the recent rise in spillovers of novel influenza A to humans, we've seen documents issued by the CDC (see CDC HAN: Accelerated Subtyping of Influenza A in Hospitalized Patients) and the ECDC (see ECDC: Updated Reporting Protocol for Zoonotic Influenza Virus) urging more aggressive testing; although these represent advisory - not regulatory - guidance.
Again last fall, in NAS : Diagnostic Tools, Gaps, and Collaborative Pathways in Human H5N1 Detection (Rapid Expert Consultation), we looked at many of the challenges inherent in detecting community cases of novel influenza.
While it is certainly worth looking for, the reality is we'll have to get very lucky if we hope to detect the early spread of a novel flu virus in the community.
