#18,166
The World Health Organization has put together a brief review of 5 recent novel flu cases reported to them between Apr 2nd and June 7th of this year, 4 of which are notable for being `first time' events due to their location, subtype, or mode of transmission.
The 5th case mentioned (H5N1 in Vietnam) is considered rare (the 1st since 2022, and only the 2nd since 2014).
Given the delays we've seen in official reporting, many of these cases actually occurred in March. At the same time, there are known cases that occurred between Apr-Jun that were not reported during that period, and are not included in this list.
A few missing cases that would fall into that range include:
There are likely other notifications still in the pipeline, or conveniently not reported.
And since the cut-off date of June 7th, we've seen a 4th H5N1 case in the United States, the CDC reported 2 New Novel Swine Flu Cases (H1N2v) In Pennsylvania, and we've seen a massive increase in the number of cattle herds infected with H5N1, and a huge spike in mammalian wildlife detections with the HPAI H5 virus.
Meanwhile, spillover and mass mortality events that would have been big news 6 months or a year ago (see Euronews - Peru | Tens of thousands of seabirds have died from bird flu), are now so common as to no longer be newsworthy.
Suffice to say, the 2nd quarter of 2024 has been an active one in the avian flu world, and while human cases remain sporadic - and we've seen no signs of efficient or sustained transmission - they are also likely under-reported (see ECDC: Enhanced Influenza Surveillance to Detect Avian Influenza Virus Infections in the EU/EEA During the Inter-Seasonal Period).
With all that in mind, we have the following synopsis from the WHO on recent, and unexpected, novel flu reports from around the globe. I'll have a bit more after the break.
Examining influenza cases reported in the past two months5 July 2024
Departmental update
Reading time: 4 min (1105 words)
Between 2 April and 7 June 2024, WHO published five Disease Outbreak News releases of influenza cases. These are summarized below looking at the date of notification, the importance of the detection, the source of exposure (how the case was infected), and the case profile (including age, sex, underlying health condition and history).
Avian Influenza A (H5N1) - Australia
Notification
On 17 May 2024, the WHO Collaborating Centre (WHO CC) for Reference and Research on Influenza in Australia notified the International Health Regulations (IHR) National Focal Point (NFP) of Australia of a suspected case of human A(H5N1) avian influenza (HPAI) in Melbourne, Victoria.
Importance
This is the first confirmed human infection caused by avian influenza A(H5N1) virus detected and reported by Australia.
Source of exposure
Although the source of exposure to the virus in this case is currently unknown, the exposure likely occurred in India, where the case had travelled, and where this clade of A(H5N1) viruses has been detected in birds.
Case profile
The case is a two and a half-year-old girl with no underlying conditions. She had a history of travel to Kolkata, India, from 12 to 29 February 2024. She returned to Australia on 1 March 2024.
Upon returning to Australia, the child presented at a hospital in Victoria on 2 March 2024, where she received medical care and was admitted on the same day. On 4 March, the patient was transferred to the intensive care unit at a referral hospital in Melbourne, Victoria, due to worsening symptoms, for a period of one week. The patient was discharged from hospital after a two and a half week admission. The case is now reported to be clinically well.
More information: https://www.who.int/emergencies/disease-outbreak-news/item/2024-DON519
Avian Influenza A (H5N2) - Mexico
Notification
On 23 May 2024, the Mexico IHR NFP reported to PAHO/WHO a confirmed case of human infection with avian influenza A(H5N2) virus in a patient with underlying co-morbidities who subsequently died.
Importance
This is the first laboratory-confirmed human with an influenza A(H5N2) detection reported globally and the first avian H5 virus detection in a person reported in Mexico.
Source of exposure
Although the source of exposure to the virus in this case is currently unknown, A(H5N2) viruses have been reported in poultry in Mexico.
Case profile
The case is a 59-year-old resident of the State of Mexico who was hospitalized in Mexico City and had no history of exposure to poultry or other animals. The case had multiple underlying medical conditions. The case’s relatives reported that the case had already been bedridden for three weeks, for other reasons, prior to the onset of acute symptoms. On 24 April, the case sought medical attention, was hospitalized, and died the same day due to complications of his condition. Although H5N2 was detected, it is not always clear what role a disease has in the death of a patient with underlying medical health issues. Further clinical and lab studies are ongoing to better understand the cause of death.
More information: https://www.who.int/emergencies/disease-outbreak-news/item/2024-DON520
Avian Influenza A(H9N2) - Viet Nam
Notification
WHO was notified about a case of human infection with an influenza A(H9N2) virus in Viet Nam on 9 April 2024 by the IHR NFP.
Importance
This is the first human infection with an avian influenza A(H9N2) virus reported in Viet Nam.
Source of exposure
Case investigation identified that the case lives near a poultry market, where poultry trade occurs daily in front of his house.
Case profile
The patient is a 37-year-old male from Tien Giang Province, Viet Nam, who had underlying conditions. The patient developed a fever on 10 March 2024 and was admitted to the hospital on 16 March. As of 15 April, the patient was still in severe condition and under intensive care.
More information: https://www
Avian Influenza A(H5N1) - United States of America
Notification
WHO was notified about a laboratory-confirmed case of human infection with an influenza A(H5N1) virus on 1 April 2024 by the United States of America IHR NFP.
Importance
This may be the first human infection with A(H5N1) acquired from contact with an infected mammal, although human infections with other influenza subtypes have previously been acquired from mammals. This is the second confirmed human case of influenza A(H5N1) detected in the country.
Source of exposure
The case, based in the state of Texas, had a history of exposure to dairy cattle (cows) presumed to be infected with influenza A (H5N1) virus. In the United States, since January 2022, detections of HPAI A(H5N1) virus among wild birds have been reported in 50 states or territories. There have been reports of sporadic A(H5) virus outbreaks among poultry and backyard flocks as well as sporadic detections in mammals and outdoor cats on the dairy facilities as reported by the United States Department of Agriculture (USDA) Animal Plant Health Inspection Service (APHIS).
Case profile
The case is aged over 18 years. On 27 March, the case developed conjunctivitis while working at a commercial dairy cattle farm. On 28 March, the patient was advised to isolate and given antiviral treatment (oseltamivir) following US CDC guidance. The patient did not report symptoms other than conjunctivitis, was not hospitalized, and at the time of reporting, was recovering.
Influenza A virus infection is exceptionally rare in bovine species. On 25 March, the USDA reported the first detection of HPAI A(H5N1) virus in dairy cattle and unpasteurized milk samples from cattle in Texas and Kansas in four dairy herds. On 29 March, USDA announced confirmation of additional detections in dairy cattle in Michigan dairy cattle that recently received cows from Texas. USDA has also announced additional confirmed detections in dairy cattle in the states of Idaho, New Mexico and Ohio. As of 9 April, USDA has announced confirmed detections on 15 farms across six states. USDA is continuing to monitor and test samples collected from other farms where cattle are displaying decreased lactation, low appetite and other signs.
More information: https://www.who.int/emergencies/disease-outbreak-news/item/2024-DON512
Avian Influenza A(H5N1) - Viet Nam
Notification
WHO was notified about a case of human infection with an influenza A(H5N1) virus on 25 March 2024 by the national authorities of Viet Nam.
Importance
This is the first human infection with an avian influenza A (H5N1) virus reported in Viet Nam since 2022.
Source of exposure
Initial results from the case investigation revealed that during the second and third weeks of February 2024, the case went bird hunting.
Case profile
The patient, a 21-year-old male with no underlying medical conditions, developed symptoms on 11 March. His condition worsened, and he was transferred to the Intensive Care Unit (ICU) of a provincial hospital. The patient died on 23 March.
More information: https://www.who.int/emergencies/disease-outbreak-news/item/2024-DON511
While there may still be some `species barrier' that protects us from an H5 pandemic (see Are Influenza Pandemic Viruses Members Of An Exclusive Club?), these viruses keep chipping away at those obstacles in unexpected ways.
Things that were once considered highly unlikely - like HPAI in cattle, spillovers into marine mammals, and H5N1 in dogs and cats - are distressingly common.
Where all of this leads is anyone's guess. We've been on the precipice before with H5N1, and it has - for unknown reasons - receded.
We may get lucky, and it may do so again.
But one of these days a novel influenza virus will kick the door in. And we'd better be ready for it when that happens.
