Health Avian flu: the next pandemic?
Catalonia Catalonia quarantines outdoor poultry farming due to an outbreak of avian flu in five wild birds
Fauna Silvestre Agriculture confirms an outbreak of avian flu in a wetland in Ávila
The Ministry of Agriculture, Fisheries and Food closely monitors
outbreaks of avian influenza
in
Spain
and establishes a guide for action in each case.
For this reason, there is a
National Avian Influenza Surveillance Program based on risk
, with an active and passive surveillance component in domestic birds and mainly passive surveillance in wild fauna.
As a result of this surveillance , nearly 10,000 samples from domestic birds and 1,000 samples from wild birds are analyzed
annually in Spain.
What is the threat of bird flu?
It is that they
mainly affect birds and occasionally manage to jump to humans
, as
Antoni Trilla
, professor of Preventive Medicine and dean of the Faculty of Medicine of the University of Barcelona, explained to this medium at the end of January.
However, the characteristics and infectious potential of these pathogens, which have demonstrated their virulence in the past, require close monitoring.
According to the evaluations of the European Center for Disease Prevention and Control (ECDC),
the risk of infection is low for the general population, being considered low/medium for those people who have frequent exposure to birds
.
This includes personnel who provide services on farms, slaughterhouses, as well as veterinary services related to poultry production.
How does avian flu develop in birds?
Avian
influenza
is a disease of birds,
caused by RNA viruses
belonging to the
Orthomyxoviridae family
, to the group known as "type A influenza".
These viruses are classified according to two types of proteins that they present on their surface for which "H" and "N" are used (for the surface antigens "hemagglutinin" and "neuroaminidase").
16 types of hemagglutinin (H1-H16) and 9 types of neuraminidase (N1-N9) are known.
The virus that is predominantly affecting Europe and that has been detected in wild birds and some cases in domestic birds in Spain is of the H5N1 subtype.
Most of these viruses cause no or mild disease and
are known as "low pathogenic viruses"
.
Viruses that are capable of producing disease and high mortality are known as "high pathogenicity viruses".
Both types of virus can be differentiated in the laboratory using molecular biology techniques (sequencing).
In what types of birds is it more frequent?
All avian species are susceptible to the disease
, including both poultry and wild birds;
within birds, hens and turkeys are more sensitive to show clinical symptoms;
geese and ducks seem to be more resistant to illness.
How does infection occur between birds?
Infected animals
excrete the virus through nasal secretions, mouth, eyes and feces.
The disease is transmitted primarily by direct contact between healthy and diseased birds, although it can also be spread by contact with contaminated materials, equipment, vehicles, or food or water.
The incubation period is 3 to 5 days
.
The clinical symptoms vary in intensity depending on the strain in question (high or low pathogenicity), and the sensitivity of the affected species (for example, galliformes are generally more sensitive than anseriforms).
In general
, it presents with depression, loss of appetite, decrease in laying, facial edema, with swollen and cyanotic combs and chins
, petechial hemorrhages in internal membranes, pancreatitis and sudden death.
How is the transmission of these animals to humans?
In general,
avian influenza viruses cannot be transmitted to humans, but the H5 and H7 subtypes can sporadically affect humans and other mammals
(some specific cases with the H9 subtype have also been described).
To date, all cases of avian influenza transmission to humans have always occurred under conditions of close direct contact with infected birds and no cases of human-to-human transmission have been reported.
What are the current outbreaks?
According to the latest report from the Ministry of Agriculture, Fisheries and Food, the Central Veterinary Laboratory of Algete has confirmed the detection of the Highly Pathogenic Avian Influenza virus (HPAI) in four new farms located in the municipalities of Carmona (Seville) and Niebla (Huelva).
With these, there
are 16 HPAI H5N1 outbreaks in poultry in Spain in 2022.
The suspicion of the disease in all cases was derived from the detection of an
abnormal increase in mortality that began between February 14 and 15
.
The samples taken by the OVS of the Junta de Andalucía were sent to the Central Veterinary Laboratory of Algete, as the National Reference Laboratory for Avian Influenza in Spain, where it has been confirmed that it is in
all cases a strain of HPAI subtype H5N1.
Current outbreaks are located here
dropdown
Below is a summary by province of the outbreaks detected so far by this wave of avian influenza, both in wildlife and in domestic birds.
Girona
: 1 case Aiguamolls de l'Empordà
Lleida:
2 cases (Riverside of the Segre River and Lleida)
Ávila:
7 cases (Lagunas del Oso, El Bohodón, Don Jimeno, Palacios Rubio and the urban area of Hoyo de Pinares, the urban area of Ávila and the urban area of Sanchidrián)
Palencia:
1 case Laguna de la Nava de Fuentes and 1 outbreak-exploitation of Fuenterrebollo turkeys
Segovia:
1 cases in Medina del Campo 2 outbreaks (laying hen farms in Íscar)
Valladolid:
6 outbreaks (1 broiler in Villarrasa, 4 outbreaks in fattening turkeys in Niebla and 1 outbreak in Trigueros fattening turkeys)
Huelva:
2 cases (Villarrasa and Almonte) and 7 outbreaks (2 Carmona fattening turkeys, 1 rearing hens in Carmona, 1 laying hens in Carmona, 1 free-range hens in El Viso de Alcor, and 2 breeding hens in Gilena)
Seville:
1 case in Marchena municipality
Cádiz:
1 case in Arcos de la Frontera
Madrid:
1 case in Guadalix reservoir
How many cases have there been in humans?
Currently, the ECDC reported a case previously confirmed as positive for avian influenza A type H5, later confirmed to be avian influenza A (H5N1).
The man in his 70s has fully recovered and no further cases have been detected among his close contacts.
From 2003 to 2021,
864 H5N1 infections have been detected
in 19 countries, 455 of which ended in patient death.
Until this year, all these infections had occurred outside Europe, mainly in Asia, but on
January 6, 2022, the United Kingdom reported the first human infection by this pathogen
identified on the continent, in an elderly man from Devon who had as pet about 20 ducks.
In
December 2020, while we were all keeping an eye on Covid, an H5N8 virus
that had decimated a
chicken farm in southern Russia
also managed to make a leap between species and, for the first time,
infected seven farm workers
.
And, in the epicenter of the outbreaks,
China, the evolution is being carefully followed, among others, of
H5N6
, which made the jump to humans for the first time in 2014 and in 2021 has accelerated the number of infections.
In these seven years it has caused 52 infections, 25 of them during the last year.
More than half of those affected died.
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