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Global Public Health Threats

5. Why is influenza the most worrisome potential global health emergency?

  • 5.1 How many people are affected by seasonal influenza?
  • 5.2 What has been the response to the new threat of avian influenza?
  • 5.3 How does WHO prepare for a worldwide outbreak?

A worldwide outbreak of influenza, or flu, is the most feared potential public health emergency of international concern. The world is already preparing for such a pandemic by strengthening the capacity of individual nations to respond to a crisis and by coordinating efforts at the international level. Measures may prevent the threat becoming a reality and may also be useful to combat other emerging health threats such as the spread of poliomyelitis and drug-resistant tuberculosis.

This text is a summary of: WHO, World Health Report 2007 – A safer future: global public health security in the 21st century (2007),
Chapter 4: Learning lessons, thinking ahead, p.45 

5.1 How many people are affected by seasonal influenza?

Seasonal influenza is caused by viruses of two main types: A and B, and the deadliest virus for humans is a subtype of influenza A. Every year, human influenza rapidly spreads around the world in seasonal epidemics, resulting in an estimated three to five million cases of severe illness and between 250 000 and 500 000 deaths. Most deaths in industrialized countries occur among people over 65 years of age

The influenza viruses change frequently, so every year it is necessary to change the composition of influenza vaccines so that they are effective for the virus in circulation. Some years, a new subtype of virus spreads, infecting a large part of the population, and potentially killing millions. This could lead to a pandemic, like the “Spanish flu” of 1918-1919 that killed an estimated 50 million people.

For the past 50 years, a wide surveillance network has been gathering information on the constantly changing strains of circulating influenza viruses. The Global Influenza Surveillance Network and FluNet guide the annual composition of recommended seasonal influenza vaccines. In addition they operate as a global early warning system because they can pick up any new influenza virus with pandemic potential and any outbreak of unusually severe illness and rapid spread.

This text is a summary of: WHO, World Health Report 2007 – A safer future: global public health security in the 21st century (2007),
Chapter 4: Learning lessons, thinking ahead, "Pandemic influenza: the most feared security threat", p.45-46 

5.2 What has been the response to the new threat of avian influenza?

Avian influenza forced the slaughter of millions of
                                        domesticated birds.
Avian influenza forced the slaughter of millions of domesticated birds.
Source: Jan Tabery

Avian influenza, also called bird flu, is an emerging epidemic disease that is highly contagious, spreads quickly and easily between domestic and wild birds, and it occasionally infects humans, although it is not passed on between humans. It presents a major threat to life, economies and security. It was first identified in Hong Kong in 1997 and since then there have been 310 reported human cases that have resulted in 189 deaths.

In Viet Nam and Thailand in 2003 and 2004 there was an outbreak of human cases of avian influenza caused by the H5N1 virus, as well as huge outbreaks in poultry. Over the following days and months, more cases of human avian influenza appeared. Most were caused by the H5N1 virus, but there were also some human infections with H7 and H9 avian influenza viruses. Tens of millions of domestic birds in many countries were destroyed to control the outbreak but, by the end of 2004 it was clear that in large parts of Asia, the virus was firmly established in poultry. In humans, 72% of the people infected with H5N1 had died by the end of 2004. Those most frequently infected were previously healthy children and young adults who had been in contact with sick or dead chickens.

In 2005, the virus passed from domestic birds to wild birds, and that gave it the ability to move over long distances. In July 2005, H5N1 reached the African continent, Central Asia, Europe and the Eastern Mediterranean Region. By 11 April 2007, 12 countries in Asia, the Middle East and Africa had reported human cases and deaths from H5N1 infection. In 2007 there were 28 cases including 14 deaths. The outbreaks in poultry continued, as did occasional cases in humans, but a virus that could be passed on from human to human did not emerge. Nevertheless, scientists agree that the threat of a pandemic persists although it is not possible to predict when it will occur, how severe it will be or which avian influenza virus will cause it.

If a fully transmissible pandemic virus emerged and it affected 25% of the world’s population as some experts have predicted, the economic and social disruption arising from so many people becoming ill at the same time throughout the world, would be disastrous.

Risk reduction measures are already in place. The most important of these is the control of H5N1 in chickens because, as long as the virus is present in chicken populations, the threat of a pandemic exists. If these measures failed and if an avian influenza virus should mutate into a form that is transmitted from human to human, the international stockpiles of anti-viral drugs would be used to treat an early focus of human-to-human transmission.

Despite these measures, the world remains poorly prepared in case of an avian influenza pandemic. The world’s capacity to produce influenza vaccines needs to be increased to create, maintain, fund and use an H5N1 vaccine stockpile effectively. Work needs to continue to develop new vaccines which could be used to prevent infection or severe illness and which, together with anti-viral drugs, might be useful to contain a worldwide outbreak.

This text is a summary of: WHO, World Health Report 2007 – A safer future: global public health security in the 21st century (2007),
Chapter 4: Learning lessons, thinking ahead, "Pandemic influenza: the most feared security threat", p.46-51 

5.3 How does WHO prepare for a worldwide outbreak?

To help countries prepare for a worldwide influenza outbreak, the WHO developed a strategic action plan with five key action areas.

  • Reducing human exposure to the H5N1 virus
  • Strengthening the early warning system
  • Intensifying rapid containment operations
  • Building capacity to cope with a pandemic
  • Coordinating global scientific research and development

By 1 May 2007, nearly all countries had a plan to prepare for an avian and human pandemic. In addition, the WHO has assisted countries that have experienced outbreaks of human cases of avian influenza, by helping to collect and test samples, infection control, medical treatment, surveillance and general organization.

It is important that animal and human health sectors cooperate at national and international levels as over 70% of new and emerging diseases originate in animals.

The response to the threat of a worldwide outbreak of influenza would be considerably stronger if several United Nations agencies worked together. For this reason, the United Nations System Influenza Coordination (UNSIC) was established in 2005 to respond to government requests for coordinated and sustained international support to implement avian and human influenza programmes.

This text is a summary of: WHO, World Health Report 2007 – A safer future: global public health security in the 21st century (2007),
Chapter 4: Learning lessons, thinking ahead, "WHO’s strategic action plan for pandemic influenza", p.52 


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