Avian Influenza and the Pandemic Threat

If the pandemic is severe, the economic impact is likely to be significant, though predictions are subject to a high degree of uncertainty, according to the International Monetary Fund.

The severity of a pandemic will depend on the illness and fatality rates, its duration, and the behavior and preparedness of households and firms, as well as the capacity and preparedness of health care systems.

A pandemic similar to the 1918 Spanish flu could result in high levels of illness and death, and a sharp but only temporary decline in global economic activity.

Disruptions

The overarching principles for the international response to disease outbreaks are included in the Revised International Health Regulations.

The Global Outbreak Alert and Response Network (GOARN) is a WHO coordinated technical collaboration of existing institutions and networks who pool human and technical resources for the rapid identification, confirmation and response to outbreaks of international importance.

The GOARN is a key international resource for implementing the International Health Regulations.

The purpose and scope of the International Health Regulations (IHR) (2005) are to "prevent, protect against, control and provide a public health response to the international spread of disease and avoid unnecessary interference with international traffic and trade."

New challenges

In recent decades, cross-border travel and trade have increased and communication technology has developed markedly. New challenges have arisen in the control of emerging and re-emerging infectious diseases.

Recent experiences with highly pathogenic H5N1 avian influenza have given the world its first advance warning that another influenza pandemic may be imminent.

Given the serious consequences of past pandemics, this advance warning has stimulated a search for ways to prevent such an event from occurring through preparedness, rapid response and containment.

Stop or slow the spread

The rapid response and containment strategy aims to stop, or at least slow the spread of pandemic influenza at the source of its emergence in order to minimize global morbidity and mortality.

Vaccines are considered the first line of defence for reducing the excess morbidity and mortality that invariably accompany pandemics.

For several reasons, no country will have adequate supplies of vaccine at the start of a pandemic and for many months thereafter. Large-scale commercial vaccine production is not expected to commence until about three to six months following the emergence of a pandemic virus.

Some drugs (known as ‘antivirals’) appear to be effective against most strains of the H5N1 virus if administered early, but there is very little real-world experience as to their effectiveness.

They include Oseltamivir (sold as Tamiflu) and Zanamivir (sold as Relenza).

These drugs are known to reduce the length of illness and complications in seasonal influenza and may also reduce the seriousness and duration of illness caused by pandemic flu.

Contingency planning for an event sometime in the future is often difficult to justify, particularly in the face of limited resources and more urgent problems and priorities.

However, there are two main reasons to invest in pandemic preparedness:

WHO has currently identified six specific phases that would cover the generation of a pandemic:

Phase 1:

No new influenza subtypes have been detected in humans. An influenza virus subtype that has caused human infection may be present in animals. The risk of human infection is considered to be low.

Phase 2:

No new influenza virus subtypes have been detected in humans. However, a circulating animal influenza virus subtype poses a substantial risk of human disease.

An influenza pandemic is a rare but recurrent event.

Three pandemics occurred in the previous century: “Spanish influenza” in 1918, “Asian influenza” in 1957, and “Hong Kong influenza” in 1968.

The 1918 pandemic killed an estimated 40–50 million people worldwide. That pandemic, which was exceptional, is considered one of the deadliest disease events in human history.

Subsequent pandemics were much milder, with an estimated 2 million deaths in 1957 and one million deaths in 1968.

Deaths

Pandemic influenza and other emerging epidemic diseases present a major threat to life, economies and security in an increasingly globalized world.

The impact of disease epidemics has increased dramatically as the world becomes ever more interconnected. For example, airlines now carry an estimated 1.6 billion passengers every year - a number equivalent to more than 20 percent of the world population.