Bird flu cases in humans the truth about the role of intensive farming

On this subject, the animal welfare associations have already issued their verdict, which is equivalent to all the others issued by animal welfare fundamentalism for any other situation: according to them, the blame for human bird flu infections lies solely and exclusively with intensive livestock farms, which will endanger the health of the entire human race, because the contagion of the next flu pandemic could start from there.

This is why, again according to them, protected livestock farms (those defined as intensive) should be closed in favour of extensive production or, better still, the production of plant food.

But as usual, it is the reality of the facts that belies these sectarian interpretations and, as always, to understand whether the avian influenza virus is capable of triggering the next pandemic in the human population we must broaden the horizon of our vision and document ourselves, not by reading the rambling statements of animal welfare associations, but by acquiring information both from the publications of the World Health Organisation and from other scientific sources.

‘We all live under the same sky, but we do not all have the same horizon’ Konrad Adenauer

For the sake of clarity, we thought of writing this article according to a question-and-answer scheme. Here they are:

Can the Avian Influenza virus infect humans?

Yes, influenza viruses generally infect mammals and birds, however, the higher receptor affinity among mammals means that human infection may come from a species belonging to this class of animals (e.g. pigs). Direct infection of humans with avian viruses is very rare, it presupposes very close contact with infected birds, and these viruses are unlikely to then infect people in contact with the sick person, the spread is therefore termed ‘in terms of effectiveness’

Are intensive livestock farms spreading the Avian Influenza virus?

No. Even if the disease does occasionally strike intensive farms, the vast majority of infections occur in the wild, among wild birds and on rural farms, where no preventive measures are taken and where there is no protection from contact with the outside environment, and, by the same token, on free-range farms, where promiscuity between wild and domestic birds is frequent in outdoor parks.

Do intensive livestock farms play a preventive role in preventing the spread of the avian influenza virus to humans and thus preventing hypothetical future pandemics?

Yes. Data from the World Health Organisation clearly show that the vast majority of human cases of Avian Influenza have occurred in people looking after poultry on rural farms. The same organisation states: We really think the biggest threat is from household poultry, there is slightly less concern when there are outbreaks of avian influenza in commercial poultry operations because they tend to have strong bio-controls in place‘.

If we look at the latest available WHO weekly report, we see that the table below shows the cases of illness due to the H5N1 virus reported in humans in south-east Asian countries since 2003 (column C) and the cases of death (column D).

Apart from the small number of cases that have occurred in 20 years (240), it cannot be overlooked that the areas of the world affected are certainly not those where intensive farming is most widespread. And that the number of cases has practically fallen to zero over time for the obvious reason that over time attention has gradually increased in effectiveness in those places too.


Why do human infections occur so frequently in South-East Asia, and why do human deaths occur mainly there?

In South-East Asia, poultry production is still mostly rural, on small farms, in unacceptable hygienic conditions, as the pictures below show:


Rural farms in Vietnam – there are multiple factors that favour human infection, possible mutation of the influenza virus and the emergence of potentially pandemic strains: very poor hygiene and promiscuity between domestic poultry, pigs and humans in areas with a high presence of wild birds, and the total absence of biosecurity measures to prevent infection.


Slaughter of domestic poultry in Laos: operators have very close contact with all kinds of organic material, without wearing any Personal Prevention Equipment (PPE).

In the situations illustrated by the photos, human infection is facilitated by close contact with a large amount of infected biological material and, in a high percentage of cases, the infected person may die.

The health situation on intensive farms is diametrically opposed. Good breeding standards, which cover structural and management aspects of the farm, prevent the vast majority of contacts with viruses from wild birds and substantially reduce the possibility of human contagion.

What factors demonstrate the preventive role of intensive poultry farming in the spread of the Avian Influenza virus to humans?

On intensive farms, there are strict biosecurity procedures that prevent unauthorised entry of people, vehicles and materials. The facilities are designed to minimise contact with the outside environment and limit access to a minimum, as the diagram and picture of a farm below clearly illustrates.

First, the farms are surrounded by a fence, and at the gate there is a disinfection arch for the very few vehicles that are allowed to enter.

Vehicles that regularly make deliveries or material pick-ups (e.g. feed deliveries, egg pick-ups) do not need to enter the farm because the silos and pick-up area are located outside the fence.

There is a refrigerator freezer to store the carcasses of dead animals so that they can be removed at the end of the production cycle, when the farm is empty. In any case, as a precaution, the freezer is also placed outside the enclosure.

Any personnel access is managed by filter zones, where the changing of clothing and, in some cases, the showering of visitors takes place. Once past the filter zone and having donned their breeding clothes, staff enter directly into the interior of all halls via closed corridors, with no further contact with the outside environment.


In many countries, vaccination against avian influenza viruses is carried out on intensive farms, and the adoption of this additional preventive measure further reduces the possibility of the virus infecting humans.

To all this we must add the fact that, thanks to intensive farming, contact between domestic birds and humans is reduced to a minimum.

Let us try to make some comparisons: on an intensive farm, a single operator can rear around 100,000 chickens under the biosecurity conditions described above. To produce the same amount of product would require 5,000 farms with 20 chickens, supervised by the same number of people, who would most likely also manage pigs and other species of animals in promiscuity.

Is monitoring for bird flu carried out on intensive farms?

Yes, according to the National Avian Influenza Control Plan, a capillary network of checks, by means of tracheal swabs, is planned every year to diagnose the possible presence of influenza viruses, even when they do not cause symptoms in animals.

In this way, the presence of the virus is immediately perceived and quickly eliminated. In this way, the entire poultry population on intensive farms is kept free of the Avian Influenza virus.

On the contrary, in rural farms, this monitoring is not carried out, due to the huge number and dispersion of small facilities on the territory


It is therefore clear that the claims of animal welfare associations that identify the sites of virus mutations and species jumps exclusively in intensive livestock farms must be rejected.

Influenza virus pandemics have plagued mankind since ancient times, when intensive farming certainly did not exist. Even a partial list of these shows us that the 1918 pandemic was certainly not the first. Throughout history, there have been other pandemics, some of which may have exceeded the lethality of the ‘Spanish’ flu. In 1510 there was a pandemic that raged through Europe. In 1580, another pandemic began in Asia, then spread to Africa, Europe and even America, it was so fierce ‘that within six weeks it afflicted almost all the nations of Europe and some Spanish cities were “almost entirely depopulated by the disease” (Beveridge, 1977). In 1688, influenza struck England, Ireland and Virginia; in all these places ‘the people were dyed as in a pestilence’ (Duffy, 1953). Europe and America were hit in 1693 and Massachusetts in 1699. In London in 1847 and 1848, more people died from influenza than from the cholera epidemic of 1832. In 1889 and 1890 there was a large and violent influenza pandemic.

We know that the influenza viruses of the successive pandemics, of 1918, 1957 and 1968, were partly of avian origin, then passed on to mammals, e.g. pigs, to become viruses suitable for infecting the human species.

What has happened since then?

Intensive livestock farms began their development phase from the 1960s onwards. People gradually moved away from the countryside, from farm life and from the dangerous proximity to many uncontrolled animal species.

Prevention activity has increased and the risk of dangerous mutations of the influenza virus has gradually decreased, but this risk remains in areas of the world where rural farming is still widespread.

Intensive livestock farms therefore play a very important role in preventing the uncontrolled spread of influenza viruses within them and, consequently, to the human population. This preventive activity is not feasible in rural and free-range farms, which are certainly not to be demonised, but accurate information must be spread about them and not distorted by biased views.

A useful tip to be properly informed on these topics is to keep up to date on the official sites of institutions such as WHO, FAO, and the OIE (now WOAH) and not to take into account information provided by biased sites (such as those of those who have invested heavily in synthetic food) or ideologically aligned sites (such as those of animal welfare associations).


The editorial staff of M.A.C.