What is avian influenza?

Avian influenza (also known as ‘bird flu’ or ‘avian flu’) is a contagious disease caused by viruses that normally infect only birds and, less frequently, pigs. These viruses do not tend to be transmitted from one species to another, but rarely, they can cross the species barrier to infect humans.

In domestic poultry, infection with avian influenza viruses causes two main forms of disease: the so-called ‘low pathogenic form’ only causes mild symptoms. The high pathogenic form spreads very rapidly, causes disease affecting multiple internal organs, and has a mortality that can approach 100%, often only within 48 hours.

What is the current situation like?

Avian influenza is not a new disease among birds. It was first identified in Italy more than a century ago. However, it was not until 1997 that international alarm was sparked about its worldwide spread.

What is special about the current outbreaks in poultry?

Current avian influenza outbreaks are highly pathogenic. They were first reported in Southeast Asia in mid-2003. They were the most severe outbreaks ever to be reported that had affected the largest number of poultry. Never before in the history of this disease have so many countries been simultaneously affected, resulting in the loss of so many birds.

The causative agent, the H5N1 virus, has proved to be especially tenacious. In spite of the deaths of million birds, the virus is considered to be endemic in different areas of the world . It is believed that several years will be needed to control thoroughly the bird flu.

What are the implications for human health?

The widespread persistence of the H5N1 virus in poultry populations poses two main risks for human health.

The first risk is that infection passes from birds to humans, resulting in very severe disease. Primary viral pneumonia and multi-organic failure are common. In the current outbreak, more than half of those infected with the virus have died.

A second risk, of even greater concern, is that the virus – if given enough opportunities – will change into a form that is highly infectious for humans and spreads easily from human to human. Such a change could mark the start of the dreaded flu pandemic.

How do people become infected?

Direct contact with infected poultry or surfaces and objects contaminated by their faeces are needed for infection to occur. Most human cases have occurred in rural or periurban areas where many households keep poultry flocks, having direct contact with humans. Exposure is considered most highly during slaughter, defeathering, butchering, and preparation of poultry for cooking. There is no evidence that properly cooked poultry or eggs can be a source of infection.

Does the virus spread easily from birds to humans?

No, the disease is not easily transmitted. It has to be borne in mind that few cases since December 2003 have occurred, although the large number of birds affected, and the numerous associated opportunities for human exposure to the virus, especially in areas where backyard flocks are common. It is not presently understood why some people, and not others, become infected following similar exposures.

Is it probable that a pandemic occurs?

Every 20 or 30 years a flu pandemic is likely to occur. Although this may not happen regularly, the last pandemic occurred only ten years after the last one (1957 and 1968, both less virulent than that of 1918).

It is a cyclical process which is produced when a subtype of a flu virus different from the one commonly circulating occurs, infecting and causing disease in humans and thus being easily transmitted.

The H5N1 virus is a new virus, which has infected humans and caused severe disease, with high mortality, but for the time being human-to-human transmission has not yet occurred. The risk that the virus will acquire this ability will persist as long as opportunities for human infection occur. These opportunities, in turn, will persist as long as the virus circulates in birds, and this situation could endure for some years to come. Today it is impossible to predict when a change enabling human-to-human transmission will occur. It is not even known if this might happen.

Have avian influenza cases been detected in Catalonia ?

At this moment no cases of infection of the H5N1 virus have been detected in Catalonia, neither in birds nor in humans.

Are there any vaccines for people?

There is currently a vaccine for birds, as the virus subtype causing outbreaks in chickens is known; but there is not yet available a vaccine for humans, as until the virus does not change and adapts to human-to-human transmission, we cannot predict how this virus will be like. However, several lines of research are being carried out by the WHO so that if a pandemic occurred, the vaccine would be available within 4-6 months.

Can the disease be cured in humans?

Two drugs can reduce the severity and the duration of the disease. Their efficacy depends on their administration within 48 hours after symptom onset.

Catalonia has 1,300,000 treatments for its population; this amount will enable to attend also risk groups, such as health professionals, security staff, and people exposed to the primary focus of infection and the environment of those likely to be infected so as to control its expansion as much as possible and give sufficient time for vaccine production.

Should the general public take the vaccine against the common flu in the current year?

The European Union, the Spanish Ministry of Health and Spanish Autonomous Communities recommend vaccination against common flu only for people included in risk groups. In Catalonia these groups include people aged 60 years and over, people in closed institutions, children and young people suffering chronic diseases, children and young people treated for a long time with acetylsalicylic acid, pregnant women and those suffering immunodeficiency, health professionals, staff in institutions treating high-risk patients, people living with high-risk people, and people carrying out essential services for the community. Therefore, the rest of the population doesn’t need to take the vaccine.

Influenza vaccination is recommended to people who want to travel to areas having reported human infection with avian flu, or areas with outbreaks in poultry if the person has to take contact with live animals. The objective of this recommendation is, on the one hand, to prevent confusion between common flu and avian flu symptoms, and on the other hand, to reduce the chances of a possible infection with the two kinds of virus (human and avian) in an individual, as this may produce a reassortment of the two viruses and create a new virus that could be as highly pathogenic as the avian virus and as easily transmitted from human to human as the common flu.

What must we do if we find a dead wild bird?

The Spanish Government has made available to the public helpline (+34) 935 617 000 to report any dead wild birds or possibly sick birds and to be informed on how to proceed. For more information, citizens can call health information helpline “Sanitat Respon” (+34 902 111 444)

Concerning poultry, you should contact the official veterinary services of regional offices adhered to the Ministry of Agriculture, Livestock and Fishing.

In cases of urban birds, principally urban pigeons, you must notify your Town council, in spite of the current epidemiological situation pigeons are not considered to be a risk.

For further information:

Action protocol to be followed in the event of a detection of a possible case of infection in human beings by the influenza virus A (H5N1)