2021
The first reported human case outside of China was detected in Laos. A five-year-old boy from Luang Prabang Province tested positive after being exposed to poultry. [13]
At least 16 isolated cases were reported in China between July and September 2021, including a case in a 26-year-old woman from Guilin who died. A 61-year-old woman who was infected in July has denied ever coming into contact with poultry. [14] [15] On 3 October, the World Health Organization said wider surveillance was urgently required to better understand the risk and the recent increase of spill over to humans. [3]
On October 26, 2021, Thijs Kuiken, a professor of comparative pathology at Erasmus University Medical Centre in Rotterdam, said the rise in human cases could be explained by a new variant which is "a little more infectious" to people. [16]
2022
On January 7, 2022, a 43-year-old woman in the Guangdong province of China was hospitalised. [17]
On January 13, 2022, five more people in the Guangxi autonomous region, the Sichuan province, and the Zhejiang province of China were reported to be infected, two of whom have died. [18]
On March 18, 2022, a 28-year-old man from Puyang in Henan Province, was hospitalized. [19]
On March 24, 2022, a 53-year-old woman from Zhenjiang City in Jiangsu Province, was hospitalized. [19]
A 56-year-old male living in Deyang City (Sichuan Province) became the 13th case of 2022 when on March 31, 2022, he developed symptoms. He was hospitalized on April 4. [20]
Avian influenza, also known as avian flu or bird flu, is a disease caused by the influenza A virus, which primarily affects birds but can sometimes affect mammals including humans. Wild aquatic birds are the primary host of the influenza A virus, which is enzootic in many bird populations.
Influenza A virus subtype H5N1 (A/H5N1) is a subtype of the influenza A virus, which causes influenza (flu), predominantly in birds. It is enzootic in many bird populations, and also panzootic. A/H5N1 virus can also infect mammals that have been exposed to infected birds; in these cases, symptoms are frequently severe or fatal.
The global spread of H5N1 influenza in birds is considered a significant pandemic threat. While other H5N1 influenza strains are known, they are significantly different on a genetic level from a highly pathogenic, emergent strain of H5N1, which was able to achieve hitherto unprecedented global spread in 2008. The H5N1 strain is a fast-mutating, highly pathogenic avian influenza virus (HPAI) found in multiple bird species. It is both epizootic and panzootic. Unless otherwise indicated, "H5N1" in this timeline refers to the 2008 highly pathogenic strain of H5N1.
Transmission and infection of H5N1 from infected avian sources to humans has been a concern since the first documented case of human infection in 1997, due to the global spread of H5N1 that constitutes a pandemic threat.
H5 N2 is a subtype of the species Influenzavirus A. The subtype infects a wide variety of birds, including chickens, ducks, turkeys, falcons, and ostriches. Affected birds usually do not appear ill, and the disease is often mild as avian influenza viral subtypes go. Some variants of the subtype are much more pathogenic than others, and outbreaks of "high-path" H5N2 result in the culling of thousands of birds in poultry farms from time to time. It appears that people who work with birds can be infected by the virus, but suffer hardly any noticeable health effects. Even people exposed to the highly pathogenic H5N2 variety that killed ostrich chicks in South Africa only seem to have developed conjunctivitis, or a perhaps a mild respiratory illness. There is no evidence of human-to-human spread of H5N2. On November 12, 2005 it was reported that a falcon was found to have H5N2. On June 5, 2024, the first confirmed human case of H5N2 was reported in Mexico.
Influenza A virus subtype H7N7 (A/H7N7) is a subtype of Influenza A virus, a genus of Orthomyxovirus, the viruses responsible for influenza. Highly pathogenic strains (HPAI) and low pathogenic strains (LPAI) exist. H7N7 can infect humans, birds, pigs, seals, and horses in the wild; and has infected mice in laboratory studies. This unusual zoonotic potential represents a pandemic threat.
Influenza A virus subtype H7N2 (A/H7N2) is a subtype of the species Influenza A virus. This subtype is one of several sometimes called bird flu virus. H7N2 is considered a low pathogenicity avian influenza (LPAI) virus. With this in mind, H5 & H7 influenza viruses can re-assort into the Highly Pathogenic variant if conditions are favorable.
H5N8 is a subtype of the influenza A virus and is highly lethal to wild birds and poultry. H5N8 is typically not associated with humans. However, seven people in Russia were found to be infected in 2021, becoming the first documented human cases.
The global spread of H5N1 in birds is considered a significant pandemic threat.
The global spread of H5N1 in birds is considered a significant pandemic threat.
Fujian flu refers to flu caused by either a Fujian human flu strain of the H3N2 subtype of the Influenza A virus or a Fujian bird flu strain of the H5N1 subtype of the Influenza A virus. These strains are named after Fujian, a coastal province in Southeast China.
H5N1 influenza virus is a type of influenza A virus which mostly infects birds. H5N1 flu is a concern due to the its global spread that may constitute a pandemic threat. The yardstick for human mortality from H5N1 is the case-fatality rate (CFR); the ratio of the number of confirmed human deaths resulting from infection of H5N1 to the number of those confirmed cases of infection with the virus. For example, if there are 100 confirmed cases of a disease and 50 die as a consequence, then the CFR is 50%. The case fatality rate does not take into account cases of a disease which are unconfirmed or undiagnosed, perhaps because symptoms were mild and unremarkable or because of a lack of diagnostic facilities. The Infection Fatality Rate (IFR) is adjusted to allow for undiagnosed cases.
The global spread of H5N1 in birds is considered a significant pandemic threat.
Influenza, commonly known as "the flu" or just "flu", is an infectious disease caused by influenza viruses. Symptoms range from mild to severe and often include fever, runny nose, sore throat, muscle pain, headache, coughing, and fatigue. These symptoms begin one to four days after exposure to the virus and last for about two to eight days. Diarrhea and vomiting can occur, particularly in children. Influenza may progress to pneumonia from the virus or a subsequent bacterial infection. Other complications include acute respiratory distress syndrome, meningitis, encephalitis, and worsening of pre-existing health problems such as asthma and cardiovascular disease.
Influenza A virus subtype H7N9 (A/H7N9) is a subtype of the influenza A virus, which causes influenza (flu), predominantly in birds. It is enzootic in many bird populations. The virus can spread rapidly through poultry flocks and among wild birds; it can also infect humans that have been exposed to infected birds.
From April to September 2017 in the Philippines, an outbreak of H5N6 avian influenza or bird flu affected poultry in at least three towns in Central Luzon; San Luis in Pampanga and Jaen and San Isidro in Nueva Ecija.
In the early 2020s, an ongoing outbreak of avian influenza subtype H5N8 has been occurring at poultry farms and among wild bird populations in several countries and continents, leading to the subsequent cullings of millions of birds to prevent a pandemic similar to that of the H5N1 outbreak in 2008. The first case of human transmission of avian flu, also known as bird flu, was reported by Russian authorities in February 2021, as several poultry farm workers tested positive for the virus.
Influenza A virus subtype H10N3 is a subtype of viruses that causes influenza (flu). It is mostly present in wild avian species. The first human case was reported in 2021.
Since 2020, outbreaks of avian influenza subtype H5N1 have been occurring, with cases reported from every continent as of May 2024. Some species of wild aquatic birds act as natural asymptomatic carriers of a large variety of influenza A viruses, which can infect poultry, other bird species, mammals and humans if they come into close contact with infected feces or contaminated material, or by eating infected birds. In late 2023, H5N1 was discovered in the Antarctic for the first time, raising fears of imminent spread throughout the region, potentially leading to a "catastrophic breeding failure" among animals that had not previously been exposed to avian influenza viruses. The main virus involved in the global outbreak is classified as H5N1 clade 2.3.4.4b, however genetic diversification with other clades such as 2.3.2.1c has seen the virus evolve in ability to cause significant outbreaks in a broader range of species including mammals.
