The impacts of influenza on human history

The first two questions face anyone who cares to distinguish the real from the unreal and the true from the false. The third question faces anyone who makes any decisions at all, and even not deciding is itself a decision.

The impacts of influenza on human history

There are many descriptions of historical outbreaks of avian influenza disseminating within domestic poultry flocks in the literature. AI occurs worldwide and different strains are more prevalent in certain areas of the world than others.

Influenza - Wikipedia

AI is a highly contagious viral disease that affects both domestic and wild birds. AI viruses have also been isolated, although less frequently, from mammalian species, including rats, mice, weasels, ferrets, pigs, cats, tigers, dogs and horses, as well as from humans. Avian influenza virus classification Influenza viruses are grouped into three types; A, B, and C.

Only type A is known to infect animals and is zoonotic, meaning it can infect animals and also humans. Type B and C mostly infect humans and typically cause mild disease. Avian influenza viruses are extremely variable and are widespread among birds.

In those, they all belong to the Orthomyxoviridae family and are placed in the genus influenzavirus A. Influenza A viruses are classified into subtypes based on two surface proteins, the hemagglutinin HA and neuraminidase NA.

At least 16 hemagglutinins H1 to H16and 9 neuraminidases N1 to N9 subtypes have been found in viruses from birds, while two additional HA and NA types have been identified, to date, only in bats.

AI virus strains are usually classified into two categories according to the severity of the disease in poultry: Low pathogenic LPAI strains, which typically cause few or no clinical signs in poultry, and may go undetected due to the lack of symptoms in some species of birds.

Highly pathogenic HPAI strains, which can cause severe clinical signs and potentially high mortality rates among poultry. To date, naturally occurring highly pathogenic influenza A viruses that produce acute clinical disease in chickens, turkeys and other birds of economic importance have been associated only with the H5 and H7 subtypes.

The impacts of influenza on human history

Molecular epidemiology and characterisation of the genotypes of AI virus in poultry and wild birds is important to understand the distribution of different viral strains in various hosts. National and OIE Reference Laboratories use molecular diagnostic techniques in the surveillance and detection of highly pathogenic strains and emergence of novel subtypes from unknown hosts or hosts that have not been previously reported.

Strains differentiation, mutation and reassortment Differentiation between low and high pathogenicity AI viruses is based on the results of laboratory tests, which are described in the OIE Manual of Diagnostic Tests and Vaccines for Terrestrial Animals.

This characterisation of AI viruses as low or high pathogenicity is specific to poultry and other birds and does not necessarily apply to other species that can be susceptible to AI viruses, including humans.

The viral HA, and to a lesser extent the NA, are major targets for the immune response. Influenza A viruses are very diverse, and two viruses that share a subtype may be only distantly related. The high variability is the result of two processes: Once these proteins have changed enough, immune responses against the former HA and NA may no longer be protective and this can provide the virus with the ability to rapidly adapt to new hosts.

The reason all H5 and H7 subtypes are reportable when detected in poultry is because there is a risk for them to become highly pathogenic by mutation. How can avian influenza be transmitted? Several factors can contribute to the spread of AI viruses, such as: In birds, AI viruses are shed in the faeces and respiratory secretions.

They can all be spread through direct contact with secretions from infected birds, especially through faeces or through contaminated feed and water. Because of the resistant nature of AI viruses, including their ability to survive for long periods when temperatures are low, they can also be carried on farm equipment and spread easily from farm to farm.

Wild birds can normally carry AI viruses in their respiratory or intestinal tracts but they do not commonly get sick, which allow them to carry the viruses on long distances along their migration flyways.

Wild birds and the global epidemiology of AI viruses Wild birds, as natural host and reservoir for all types of avian influenza viruses, play a major role in the evolution, maintenance, and spread of these viruses.

The impacts of influenza on human history

The main wild species involved have proved to be waterfowls, gulls, and shorebirds, however the virus seem to pass easily between different bird species.

The incidence of infection appears to be seasonal, with the highest isolation rate being in juvenile birds in the fall of the year. Several routes of exposure of wild bird viruses to poultry have been documented or suspected of being the origins of outbreaks.

Direct exposure to wild birds is the most likely transmission factor. Therefore, limiting exposure of poultry to wild birds through confinement rearing and other biosecurity measures provides an opportunity to reduce the risk of introduction of avian influenza virus from wild birds, and consequently is key to decrease the risk of evolution into highly pathogenic forms, exposure and infection of humans, and recombination with human viruses components to form viruses that can not only infect humans but readily transmit among humans.

Devastating economic consequences Avian Influenza outbreaks can lead to devastating consequences for the poultry industry as well as at national level.

Experience has shown that: Potential of human infection People who are in close contact with infected birds are at risk for acquiring avian influenza. While many human cases are limited to conjunctivitis or mild respiratory disease, some viruses tend to cause severe illness.

However, there is no evidence to suggest that the consumption of poultry or eggs fit for human consumption could transmit the AI virus to humans. As a precautionary and regulatory measure, animals that have been culled as a result of measures to control an AI outbreak should not be allowed to enter the human food and animal feed chain, and precautionary measures for the cleaning and cooking process should be respected.Recommendations for laboratory procedures to detect avian influenza A H5N1 virus in specimens from suspected human cases WHO Geneva • August In pigs, horses and dogs, influenza symptoms are similar to humans, with cough, fever and loss of appetite.

The frequency of animal diseases are not as well-studied as human infection, but an outbreak of influenza in harbor seals caused approximately seal deaths off the New England coast in – Avian influenza (bird flu) mainly affects birds. It can also affect humans and other mammals.

Bird flu is a notifiable animal disease. If you suspect any type of bird flu you must report it. The global scale, interconnectedness, and economic intensity of contemporary human activity are historically unprecedented, 1 as are many of the consequent environmental and social changes.

These. The Spanish influenza pandemic, which stands as the single most fatal event in human history, killed an estimated 50 million people or more globally. 14 As noted, the causative agent was an avian-descended H1N1 virus and a direct progenitor of all of the influenza A viruses circulating in humans today.

2, 3 The high mortality associated with. The human impact on natural ecosystems has reached dangerous levels, even significantly altering the Earth's basic chemical cycles, says a new report, World Resources People and Ecosystems, The Fraying Web of Life.

The report paints a dismal picture of over-fished oceans, over-pumping of water for farming, destruction of coral reefs and forests, even too much tourism, with human.

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