Bird flu

The bird flu or bird flu, also called avian influenza, chicken flu > or bird flu, designates a viral infectious disease that affects birds, although it has sufficient potential to infect different species of mammals, including humans, pigs and cats domestic. It was first identified in Italy at the end of the 19th century and to date it has manifested itself in various parts of the world.

Avian influenza viruses are subtypes of Influenza A virus and are part of the genus Alphainfluenzavirus of the family Orthomyxoviridae and are negative-stranded segmented RNA virus. This family includes several viruses classified into three types, A, B, or C, based on the antigenic character of an internal nucleoprotein. Type A is the only one that causes natural infections in birds. Types B and C primarily infect humans and occasionally pigs.

History

The highly pathogenic avian flu was first described in Italy in 1878. It was also known as the Lombardy disease. Although Eugenio Centanni (1863-1942) and Ezio Savonuzzi, in 1901, identified a responsible agent as the cause of the disease, it was not until 1955 that Werner Schäfer (1912-2000) described it as a virus of the Influenzavirus A type. In its reservoir naturally occurring in waterfowl, the infection is usually asymptomatic.

The first association of the H5N1 virus with respiratory diseases occurred in Hong Kong in 1997, when 18 human cases, during an epidemic of the H5N1 pathogen, were described in live bird markets. This epidemic was characterized by a high mortality rate (up to 33%), a high incidence of pneumonia (61%), and a high incidence of cases requiring care in respiratory care units (51%).

All of the virus genes were of avian viral origin, suggesting that H5N1 had jumped the intraspecific barrier. Serological surveillance reveals little evidence of human-human transmission.

In February 2021, Russia alerted the WHO of the first case of the H5N8 strain transmitted to a human being.

In January 2022, massive outbreaks were recorded in countries such as Israel, Spain and France, among others.

United Kingdom ratifies a case of a human being infected by the H5N1 bird flu Contagion in humans by the H5N1 bird flu

Description of the disease in birds

Highly Pathogenic Avian Influenza is a viral disease caused by some subtypes (H5 and H7) of type A of the influenza virus, belonging to the Orthomyxoviridae family that affects most avian species, causing systemic disease. and extremely contagious, with a high twenty-four-hour mortality in commercial poultry farms and therefore can have a very decisive influence on the production and marketing of poultry and poultry products in a territory or a country. The disease is caused by a type A influenza virus. Its potential to infect humans has recently been discovered.

Influenza A viruses are further divided into subtypes based on the hemagglutinin and neuraminidase proteins. There are sixteen types of hemagglutinins and nine different subtypes of neuraminidase, giving one hundred and forty-four different combinations of H and N. All subtypes are capable of infecting birds, but not of causing disease. To date, all outbreaks of the hyperpathogenic form have been caused solely by the H5 and H7 subtypes (endowed with hemagglutinin variants 5 and 7).

Migratory waterfowl, especially wild ducks, are the natural reservoir of avian influenza viruses, and these birds are also the most resistant to infection. Domestic poultry are the most vulnerable to these withering flu epidemics. The mallard is an important reservoir of the virus, being in contact with humans in lakes and ponds. It houses the sixteen hemagglutinin subtypes (except H13 and H16) and the nine neuroamindase subtypes that are part of viruses.

It is capable of maintaining viability in the environment for long periods of time, especially when temperatures are low, although it is known not to survive temperatures above 70 °C or below -80 °C

The bird flu virus can affect a large number of bird species including poultry and wild birds; although susceptibility to disease is highly variable. The birds with a greater susceptibility to infection, and therefore to the appearance of the disease, are gallinaceous birds. The ducks are susceptible, but in many cases the process is subclinical and they act as carriers.

Once the virus has been introduced into a farm, when it is excreted in faeces and respiratory secretions, its transmission and diffusion occurs mainly in the following way:

• Direct contact with secretions of infected birds, especially feces.
• Food, water, equipment and contaminated clothing.
• Airway.

It has been established that transmission from one farm to another, in the outbreaks that occurred in Italy (1999) and the Netherlands (2003), occurred by the following means:

• Aerogena (1 km between farms).
• People and teams.
• Transport of contaminated eggs, food or hen.

Bird flu viruses do not usually infect other animals. The first known case of human infection with avian influenza virus occurred in Hong Kong in 1997, when the H5N1 strain caused severe respiratory illness in eighteen people. That infection coincided with an epidemic of highly pathogenic bird flu, caused by the same strain.

The rapid culling, over three days, of Hong Kong's entire poultry population, estimated at approximately 1.5 million animals, reduced the chances of direct transmission to humans and the virus could be contained temporarily.

In humans, since H5N1 is an influenza virus, symptoms can resemble the common flu, with fever, cough, dry throat, and myalgias (muscle pain). However, in more severe cases, pneumonia and severe respiratory problems can develop, and can eventually cause death. Patients infected with H5N1 have presented few cases of conjunctivitis, unlike human cases of the H7 virus.

Pandemics

The World Health Organization (WHO) (2005) has warned of a substantial risk of a global epidemic (pandemic) of influenza in the near future, with the highest probability arising from the H5N1 type of avian influenza. The risk is based on the form of recombination between the avian influenza virus and some of the viruses that circulate in the human population, however, there is currently no evidence of this and it is more of an assumption for global health prevention.

Global spread 2004-2006

Extension of avian flu until 26 October 2005. It does not yet include outbreaks in Colombia, Mexico and Nigeria.

Africa

In February 2004, the H5N1 strain was discovered for the first time on the African continent, specifically in Nigeria. According to the Nigerian National Veterinary Institute, up to 40% of poultry barns may be infected.

Asian

In July 2004 new apparitions were confirmed in the Thai provinces of Ayutthaya and Pathumthani, as well as in the city of Anhui in China.

In August 2004 cases of bird flu appeared in Kampung Pasir, Kelantan, Malaysia. Two chickens carried H5N1. As a consequence, Singapore imposed a ban on all imports of chicken and other poultry products. Similarly, the European Union has banned poultry products from Malaysia. The Malaysian government ordered the collection of all poultry within a 10 km radius of the point where the virus was detected for slaughter. The move appears to have been successful, and Singapore has since lifted the ban and Malaysia has asked the Office International des Epizooties (world organization for animal health based in Paris, France) to declare Malaysia free of bird fever...

Another outbreak of bird flu in January 2005 affected 33 of 64 cities and provinces in Vietnam, leading to the slaughter of almost 1.2 million poultry. It is believed that up to 140 million birds may have died or been culled from the epidemic.

Human cases

In Vietnam and Thailand, there have been isolated cases of suspected human-to-human transmission of the virus. In one case, the girl who received the virus from a bird was in the care of her mother for about 5 days until she died. Soon after, her mother fell ill and died as well. In March 2005 it was revealed that two nurses who had cared for bird flu patients had tested positive for the virus.

There is also concern about bird migration. In the summer of 2005, H5N1 occurrences were reported in northwestern China and eastern Russia. European media and some government officials have expressed concern that the virus is moving west. However, a June 2006 communication in the New England Journal of Medicine revealed that the first H5N1 death occurred in November 2003 and that the virus strain was the same as the observed in Vietnam and Thailand, different from Hong Kong in 1997.

In June 2006, at a meeting of experts in Jakarta, it was revealed that the WHO experts considered it very probable that the first contagion or case of transmission between humans had occurred, in a family from the town of Karo in Sumatra, where eight members they were infected in May 2006.^{[citation needed]} The episode began with the infection of a woman, who in turn would have transmitted the disease to seven other members of her family, after prolonged contact in the later stages of the disease.^{[citation needed]}

On January 3, 2014, a person in Canada died of H5N1 a few days after being infected. The patient was the first detected in North America. He himself had previously traveled to Beijing, China.

Europe

Cases in birds

In October 2005 the first case of H5N1 was confirmed in the European Union (a quarantined parrot in Great Britain) and a few days later also in Croatia (in swans). In February 2006, bird flu spread through Italy, Greece, Austria, Germany, Hungary, Slovakia, Slovenia and France. In July 2006 the first case of bird flu in Spain was confirmed.

Mammalian cases

At the end of February 2006, on the German island of Rügen, in the Baltic Sea, the first case in Europe of an H5N1 infection transmitted to a mammal was detected, specifically a cat found dead. For this reason, it was recommended to isolate cats and other domestic animals from contact with the outside in those areas where outbreaks (WN) had occurred. In an Austrian shelter known as Noah's Ark, where 32 birds had previously been culled, three more cases were discovered in cats. The animals were transferred to Vienna for examination (WN).

America

Outbreak in Higüey, Dominican Republic

In January 2008, the Dominican Republic announced the appearance in Higüey to the east of the island of the H5N1 bird flu strain, of low pathogenicity. The cases were discovered when some poultry producers requested official permission to export fighting cocks to Colombia.

Outbreak in Chiapas, Jalisco, Sonora and Nuevo León, Mexico

In January 2006, an outbreak of the H5 bird flu strain was detected in the impoverished rural areas of the Mexican state of Chiapas. According to the Food and Agriculture Organization (FAO), this strain is not transmissible to humans and the outbreak is not related to the crisis in Turkey that occurred almost simultaneously.

In 2022, Mexico reported a first case of the severe H5N1 strain of avian flu, reported the World Organization for Animal Health (OMSA) in a wild bird in the municipality of Metepec, in the State of Mexico and in poultry farms of Jalisco, Sonora and Nuevo León.

Outbreak in Bahamas

(March 6, 2006): In the Inagua National Park, an island in the southern Bahamas archipelago, 10 dead migratory pink flamingos were found, as well as 5 spoonbills and some cormorants. The risk is considerable, given that the flamingo population in that specific area is 50,000 birds, in addition to being a station area for a large number of migratory birds, mainly ducks and geese, who have a marked migratory behavior, covering distances extremely large. It should be noted that it would be the first case of H5N1 in the Americas, constituting a greater risk for Central and North America, since practically all the geese and ducks that transit through that area go north, never passing through South America. The confirmation of the strain is in charge of the Bahamian authorities, supposedly during the current week.

Outbreak in Colombia

On October 6, 2005, Colombia announced the appearance of the H9 low-intensity avian flu strain on three farms in Fresno, Tolima department. Although the strain is not identified as transmissible to humans, the outbreak has earned Colombia the imposition of a commercial quarantine by its neighbors.

Production of medicines in Brazil

The government of Lula da Silva stated at the time that it was willing to ignore the patent laws for the antiviral drug Tamiflu in the event of an epidemic, something they already did in the case of drugs to treat the AIDS virus (HIV)..

A virus in constant mutation

Recent research has shown that low pathogenic viruses can, after circulating for sometimes brief periods in a poultry population, mutate and become highly pathogenic viruses. Currently, according to studies by the National Center for Biotechnology, the virus could evolve in such a way that it could be spread between humans. In this sense, an exceptional case of contagion from a patient to two relatives was recorded in Cambodia in 2004. For a form with transmissibility between humans to appear, it is necessary for the surface antigens (haemagglutinin and neuraminidase) to mutate to adapt to the specificity of human cell membranes, rather than avian ones. In addition, the form of contagion could evolve from direct contact to airborne mode.

All influenza A viruses, including those that cause seasonal epidemics in humans, are genetically adept and well adapted to evade host defenses. Influenza viruses lack replication error repair mechanisms. As a result, the genetic composition of viruses changes as they replicate in humans and animals, and the starting strain is replaced by a new antigenic variant. These constant and usually small changes in the antigenic composition of influenza A viruses is called antigenic drift.

Influenza A strain, including subtypes from different species, can exchange or recombine genetic material and fuse. This recombination process, known as antigenic shift, results in a new subtype different from the two original viruses.

Virulence on the rise

In July 2004, researchers led by H. Deng of the Harbin Veterinary Research Institute in China and Professor Robert Webster of St Jude Children's Research Hospital in Memphis, Tennessee, reported the results of their experiments in which laboratory mice had been exposed to 21 confirmed extracts of H5N1 strains extracted from ducks in China between 1999 and 2002. They found "a clear pattern of progressive incremental pathogenicity". Additional results from Dr. Webster in July 2005 reveal greater progression towards pathogenicity in mice and longer virus extractions in ducks.

Treatment

Although there are no treatments capable of producing a true cure against an avian flu infection, there are drugs capable of stopping the development of the virus. Neuraminidase inhibitors such as oseltamivir and zanamivir, which act on a protein conserved in all influenza A viruses, are used against the developing avian influenza virus (H5N1).

Oseltamivir is distributed by Roche (Hoffmann-La Roche) laboratories as Tamiflu, and has become the medicine of choice for governments and organizations to prepare for the possibility of a pandemic. In August 2005 Roche agreed to donate three million doses of Tamiflu to the World Health Organization, so that the WHO can try to contain the pandemic at the source.

M2 inhibitors are another class of drugs that include amantadine and rimantadine. Unlike zanamivir and oseltamivir, these drugs are not very expensive and are easily available. The WHO had originally planned to prepare with such drugs, but plans were reversed when it emerged that the PRC had been administering amantadine to its poultry with government support since the early 1990s, contrary to international regulations.. As a result of this, the virus strain currently circulating in Southeast Asia is virtually immune to the drug and therefore potentially more dangerous to humans. However, the H5N1 strain that spread across northern China, Mongolia, Kazakhstan, and Russia by wild birds in the summer of 2005 is not resistant to amantadine.

Prevention

The current method of prevention in animal populations is to destroy infected and suspected infected animals. To date millions of domestic birds have been culled in Southeast Asia.

The US government's Centers for Disease Control and Prevention is advising people planning to travel to countries where H5N1 has been detected to avoid poultry farms and food markets. with live animals. Travelers should avoid surfaces that appear to be contaminated by feces from any animal, especially birds. Another means of prevention is to avoid areas where fights between animals are exhibited. Cultures that perform rituals with animals that potentially carry the disease are also a source of danger.

Vaccine

In August 2005, scientists said they had successfully tested a vaccine on humans that is believed to protect people from the bird flu strain spreading in birds in Asia and Russia.

On October 19, 2005, Hungary's health minister, Jenij Racz, announced that his country had developed a vaccine against the H5N1 virus. This vaccine would have been developed from a sample of the virus obtained in Hong Kong in 1997 and isolated in 2005 by the WHO. However, the characteristics of the virus strain that affects humans are unknown.

On April 19, 2007, the FDA of the United States of America approved the first vaccine against avian influenza for the H5N1 virus, which can be used in humans, Sanofi Pasteur is the group that markets the vaccine, there are other laboratories such as Glaxo Smith Kline called the vaccine Daronrix, Focetria from Novartis pharmaceutical laboratories. Reportedly, the vaccine protects in 45% of those vaccinated.