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Preparedness
An
influenza pandemic
A
new influenza virus: how it could cause a pandemic
Outbreaks
of influenza in animals
Consequences
of an influenza pandemic
If
an influenza pandemic appears, we could expect
the following
Detecting
a new pandemic virus
Preparing
for an influenza pandemic
An influenza pandemic
An influenza pandemic occurs when a new influenza
virus appears against which the human population
has no immunity, resulting in several, simultaneous
epidemics worldwide with enormous numbers of deaths
and illness. With the increase in global transport
and communications, as well as urbanization and
overcrowded conditions, epidemics due the new
influenza virus are likely to quickly take hold
around the world.
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A new influenza virus: how it could cause
a pandemic
Annual outbreaks of influenza are due to minor
changes in the surface proteins of the viruses
that enable the viruses to evade the immunity
humans have developed after previous infections
with the viruses or in response to vaccinations.
When a major change in either one or both of their
surface proteins occurs spontaneously, no one
will have partial or full immunity against infection
because it is a completely new virus. If this
new virus also has the capacity to spread from
person-to-person, then a pandemic will occur.
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Outbreaks of influenza in animals
Outbreaks of influenza in animals, especially
when happening simultaneously with annual outbreaks
in humans, increase the chances of a pandemic,
through the merging of animal and human influenza
viruses. During the last few years, the world
has faced several threats with pandemic potential,
making the occurrence of the next pandemic just
a matter of time.
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Consequences of an influenza pandemic
In the past, new strains have generated pandemics
causing high death rates and great social disruption.
In the 20th century, the greatest influenza pandemic
occurred in 1918 -1919 and caused an estimated
40–50 million deaths world wide. Although
health care has improved in the last decades,
epidemiological models from the Centers for Disease
Control and Prevention, Atlanta, USA project that
today a pandemic is likely to result in 2 to 7.4
million deaths globally. In high income countries
alone, accounting for 15% of the worlds population,
models project a demand for 134–233 million
outpatient visits and 1.5–5.2 million hospital
admissions. However, the impact of the next pandemic
is likely to be the greatest in low income countries
because of different population characteristics
and the already strained health care resources.
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If an influenza pandemic appears, we could
expect the following
Given the high level of global traffic, the pandemic
virus may spread rapidly, leaving little or no
time to prepare. Vaccines, antiviral agents and
antibiotics to treat secondary infections will
be in short supply and will be unequally distributed.
It will take several months before any vaccine
becomes available. Medical facilities will be
overwhelmed. Widespread illness may result in
sudden and potentially significant shortages of
personnel to provide essential community services.
The effect of influenza on individual communities
will be relatively prolonged when compared to
other natural disasters, as it is expected that
outbreaks will reoccur.
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Detecting a new pandemic virus
Continuous global surveillance of influenza is
key. WHO has a network of 112 National Influenza
Centres that monitors influenza activity and isolates
influenza viruses in all continents. National
Influenza Centres will report the emergence of
an “unusual” influenza virus immediately
to the WHO Global Influenza Programme or to 1
of the 4 WHO Collaborating Centres. Rapid detection
of unusual influenza outbreaks, isolation of possible
pandemic viruses and immediate alert to the WHO
system by national authorities is decisive for
mounting a timely and efficient response to pandemics.
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Preparing for an influenza pandemic
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:
1. Preparation will mitigate the direct medical
and economic effects of a pandemic, by ensuring
that adequate measures will be taken and implemented
before the pandemic occurs.
2. Preparing for the next influenza pandemic
will provide benefits now, as improvements in
infrastructure can have immediate and lasting
benefits, and can also mitigate the effect of
other epidemics or infectious disease threats.
A major component of pandemic preparedness is
to strengthen the capacity to respond to yearly
epidemics of influenza. A surveillance network
for human and animal influenza and a targeted
influenza vaccination programme are the cornerstones
of a national influenza policy.
Ensuring an adequate system for alert, response
and disaster management, should be the basis of
every national pandemic preparedness plan. Depending
on the available resources, more specific preparations
can be made, such as developing specific contingency
plans, stockpiling of antivirals, strengthening
risk communications, investing in pandemic vaccine
research and promoting domestic production of
influenza vaccines.
WHO has developed a global influenza preparedness
plan, which defines the responsibilities of WHO
and national authorities in case of an influenza
pandemic. This plan incorporates new scientific
data and experience obtained during recent outbreaks
that had pandemic potential. WHO also offers guidance
tools and training to assist in the development
of national pandemic preparedness plans.
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