Influenza World

Often the term ‘bird flu’ – (also known as avian flu) – is used to refer to three different phenomena:

• bird flu in birds
• bird flu in humans
• pandemic flu. [1]

However, bird flu and pandemic flu are two different things. Both are a threat, but the threats they pose to human and animal health are distinct.

Bird flu in birds

Bird flu is a disease caused by avian flu viruses. Wild birds carry these flu viruses naturally in their intestines, without developing disease symptoms. However, these flu viruses spread easily among birds and can make some domestic birds, including chickens, ducks and turkeys, very sick and kill them.

Bird flu viruses that attack domestic poultry are distinguished by the severity of the disease they cause:

• Less severe form (low pathogenic) – causes mild symptoms (such as ruffled feathers and a drop in egg production). May go undetected.
• Highly severe form (highly pathogenic) – spreads rapidly throughout flocks of poultry and may cause disease that affects multiple internal organs and has been known to kill in nearly all cases, often within 48 hours. [2] One example of a highly pathogenic form of bird flu virus is the H5N1 strain that has also infected humans.

Bird flu in humans

The risk from bird flu is generally low among most people because the viruses do not usually infect humans. However, during an outbreak of bird flu among poultry, there is a possible risk to people who have had close contact with the sick birds themselves or surfaces that have been contaminated with their secretions or excretions.

So far, the spread of bird flu from human-to-human has been limited. Nonetheless, because all flu viruses are able to change – or mutate – scientists are concerned that one day the H5N1 virus could infect and spread easily among humans.

Why the concern about H5N1?

Currently there is no pandemic flu. However, the continued spread of the highly pathogenic bird flu strain H5N1, from South East Asia into other countries, such as Sub-Saharan Africa, Egypt and Turkey, has raised concerns about a potential human pandemic . H5N1 bird flu strain has caused the death or destruction of tens of millions of birds, and, as of 11 April 2007, had caused 291 cases of bird-to-human transmission and 172 deaths since 2003. [3] More than half of those infected with H5N1 have died. This high death rate is one of the reasons why experts and public health authorities are so concerned. If H5N1 virus were to gain the capacity to spread easily from one person to another, a deadly flu pandemic could begin.

What is being done to monitor the spread of bird flu?

It is important to know where disease outbreaks begin and understand how and where they may spread to. The main aim of bird flu monitoring is to identify any cases of human-to-human transmission quickly, so that health officials can attempt to contain and control the outbreak. The World Health Organization (WHO) has surveillance systems in place to monitor and track bird flu outbreaks, and to enable the co-ordination of the global response to human cases of H5N1 flu. Their website shows disease maps that track the incidence of bird flu and which countries have been affected.

1. Pan American Health Organization. Avian vs. pandemic flu: understanding the threat (press release). Available here.
2. Centres for Disease Control and Prevention. Key facts about avian influenza (bird flu) and avian influenza A (H5N1) virus. Available here.
3. World Health Organization. Cumulative number of confirmed human cases of avian influenza A/(H5N1) reported to WHO. Available here.