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Between 2003 and 2016 the world saw more than 860 H5N1 cases, with the large multi-month surge in Egypt in the spring of 2015 being the largest outbreak recorded (see EID Dispatch: Increased Number Of Human H5N1 Infection – Egypt, 2014-15).
In truth, we don't really know how many human infections occurred, or H5N1's fatality rate (see Revisiting the H5N1 CFR (Case Fatality Rate) Debate). Many cases were likely missed, or went unreported.
After the Egyptian outbreak, the number of cases declined dramatically and out attentions were drawn towards MERS-CoV and the rising toll of avian H7N9 in China, and later, the coronavirus pandemic. But over the past year, H5N1 has made a bit of a comeback as it has spread globally.
With the news of 2 cases this week in Cambodia, and the recent case in Ecuador - along with increased spillover of the virus into mammalian wildlife - fresh attention is being paid to H5N1.
Today the ECDC has published, in their weekly CDT Report, an update on H5N1 and a new risk assessment. For now, the risk to the general public from H5N1 remains Low.
Influenza A(H5N1) - Multi-country (World)- Monitoring human casesOverview
Update:
On 23 February 2023, one fatal case of avian influenza A(H5N1) was reported in Sithor Kandal district, Prey Veng province, Cambodia. The 11-year-old girl from Roleang village developed symptoms on 16 February 2023, was hospitalised three days later and died on 22 February. According to the report from the Ministry of Health of Cambodia (MoH), a traditional funeral was performed.
According to the Ministry of health of Cambodia, samples were taken from 12 people, four of whom developed respiratory symptoms. One of these samples was positive to A(H5N1), from a 49-year-old man, the father of the first case. The second case did not report any significant symptoms.
According to a media report, the family reported deaths of backyard poultry.
In addition, on 17 February, samples were taken from wild birds in the village following reports of deaths (report from MoH). An educational communication campaign has been initiated by the Ministry of Health with precautionary measures to avoid infection and to seek immediate medical attention in case of symptoms.
This is the first event of avian influenza A(H5N1) detected in humans in Cambodia since 2014. In the past, Cambodia reported 56 cases including 37 deaths between 2005 and 2014. Overall, there have been 58 cases with avian influenza A(H5N1) infection, including 38 deaths reported in Cambodia.
Summary:
As of 23 February 2023, there have been 870 cases, including 458 deaths (CFR: 52.6%), of human infection with avian influenza A(H5N1) reported in 21 countries. To date, no human-to-human transmission has been detected.
Sources:
ECDC Avian influenza, ECDC Avian influenza overview: Latest situation update of the avian influenza in EU/EEA, the Ministry of Health of Cambodia, media report 1, media report 2, media report 3 SURVEILLANCE REPORT Weekly Communicable Disease Threats Report, Week 8, 19 - 25 February 2023 6ECDC assessment:
Sporadic human cases of different avian influenza A(H5Nx) subtypes have been previously reported globally. A family cluster of infection with A(H5N1) in humans is reported in Cambodia, the investigation is ongoing to identify the source of infection amid the reports from health authorities about sick and dead backyard poultry and wild birds detected in the residential area of this family. More information about the exposure as well as viral sequences is needed to better understand the circumstances of the transmission to humans.
Current epidemiological and virological evidence suggests that A(H5N1) viruses reman avian-like. Transmission to humans remains a rare event and no sustained transmission between humans has been observed. The risk of zoonotic influenza transmission to the general public in EU/EEA countries remains the same and is considered to be low. The risk to occupationally exposed groups such as cullers has been assessed as low to medium.
Direct contact with infected birds or a contaminated environment is the most likely source of infection and the use of personal protective measures for people exposed to dead birds or their droppings will minimise the remaining risk. The recent severe cases in Asia and South America in children and people exposed to infected sick and dead backyard poultry underline the risk associated with unprotected contact to infected birds in backyard farm settings and suggests the appropriate use of personal protective equipment.
Actions
ECDC is in contact with WHO and other partners to obtain more information on the current event in Cambodia. ECDC monitors avian influenza strains through its influenza surveillance programme and epidemic intelligence activities in collaboration with EFSA and the EU reference laboratory for avian influenza, in order to identify significant changes in the virological characteristics and epidemiology of the virus. ECDC, together with EFSA and the EU reference laboratory for avian influenza, produces a quarterly updated report of the avian influenza situation. The most recent report was published on 20 December 2022.
