Influenza pandemic (H1N1) 2009 (37): 2nd wave plan, WHO
Date: Fri 28 Aug 2009
Source: World Health Organization (WHO)
Global Alert and Response (GAR)
Pandemic (H1N1) 2009 Briefing note 9. [edited]
<http://www.who.int/csr/disease/swineflu/notes/h1n1_second_wave_20090828/en/index.html>
Preparing for the 2nd wave: lessons from current outbreaks Pandemic (H1N1)
2009
-------------------------------------------------------------------------------
Monitoring of outbreaks from different parts of the world provides
sufficient information to make some tentative conclusions about how the
influenza pandemic might evolve in the coming months. WHO is advising
countries in the northern hemisphere to prepare for a 2nd wave of pandemic
spread. Countries with tropical climates, where the pandemic virus arrived
later than elsewhere, also need to prepare for an increasing number of
cases. Countries in temperate parts of the southern hemisphere should
remain vigilant. As experience has shown, localized "hot spots" of
increasing transmission can continue to occur even when the pandemic has
peaked at the national level.
H1N1 now the dominant virus strain
----------------------------------
Evidence from multiple outbreak sites demonstrates that the H1N1 pandemic
2009 virus has rapidly established itself and is now the dominant influenza
strain in most parts of the world. The pandemic will persist in the coming
months as the virus continues to move through susceptible populations.
Close monitoring of viruses by a WHO network of laboratories shows that
viruses from all outbreaks remain virtually identical. Studies have
detected no signs that the virus has mutated to a more virulent or lethal form.
Likewise, the clinical picture of pandemic influenza is largely consistent
across all countries. The overwhelming majority of patients continue to
experience mild illness. Although the virus can cause very severe and fatal
illness, also in young and healthy people, the number of such cases remains
small.
Large populations susceptible to infection
------------------------------------------
While these trends are encouraging, large numbers of people in all
countries remain susceptible to infection. Even if the current pattern of
usually mild illness continues, the impact of the pandemic during the 2nd
wave could worsen as larger numbers of people become infected. Larger
numbers of severely ill patients requiring intensive care are likely to be
the most urgent burden on health services, creating pressures that could
overwhelm intensive care units and possibly disrupt the provision of care
for other diseases.
Monitoring for drug resistance
------------------------------
At present, only a handful of pandemic viruses resistant to oseltamivir
have been detected worldwide, despite the administration of many millions
of treatment courses of antiviral drugs. All of these cases have been
extensively investigated, and no instances of onward transmission of
drug-resistant virus have been documented to date. Intense monitoring
continues, also through the WHO network of laboratories.
Not the same as seasonal influenza
----------------------------------
Current evidence points to some important differences between patterns of
illness reported during the pandemic and those seen during seasonal
epidemics of influenza. The age groups affected by the pandemic are
generally younger. This is true for those most frequently infected, and
especially so for those experiencing severe or fatal illness. To date, most
severe cases and deaths have occurred in adults under the age of 50 years,
with deaths in the elderly comparatively rare. This age distribution is in
stark contrast with seasonal influenza, where around 90 percent of severe
and fatal cases occur in people 65 years of age or older.
Severe respiratory failure
--------------------------
Perhaps most significantly, clinicians from around the world are reporting
a very severe form of disease, also in young and otherwise healthy people,
which is rarely seen during seasonal influenza infections. In these
patients, the virus directly infects the lung, causing severe respiratory
failure. Saving these lives depends on highly specialized and demanding
care in intensive care units, usually with long and costly stays.
During the winter season in the southern hemisphere, several countries have
viewed the need for intensive care as the greatest burden on health
services. Some cities in these countries report that nearly 15 per cent of
hospitalized cases have required intensive care. Preparedness measures need
to anticipate this increased demand on intensive care units, which could be
overwhelmed by a sudden surge in the number of severe cases.
Vulnerable groups
-----------------
An increased risk during pregnancy is now consistently well-documented
across countries. This risk takes on added significance for a virus, like
this one, that preferentially infects younger people. Data continue to show
that certain medical conditions increase the risk of severe and fatal
illness. These include respiratory disease, notably asthma, cardiovascular
disease, diabetes and immunosuppression. When anticipating the impact of
the pandemic as more people become infected, health officials need to be
aware that many of these predisposing conditions have become much more
widespread in recent decades, thus increasing the pool of vulnerable people.
Obesity, which is frequently present in severe and fatal cases, is now a
global epidemic. WHO estimates that, worldwide, more than 230 million
people suffer from asthma, and more than 220 million people have diabetes.
Moreover, conditions such as asthma and diabetes are not usually considered
killer diseases, especially in children and young adults. Young deaths from
such conditions, precipitated by infection with the H1N1 virus, can be
another dimension of the pandemic's impact.
Higher risk of hospitalization and death
----------------------------------------
Several early studies show a higher risk of hospitalization and death among
certain subgroups, including minority groups and indigenous populations. In
some studies, the risk in these groups is 4 to 5 times higher than in the
general population. Although the reasons are not fully understood, possible
explanations include lower standards of living and poor overall health
status, including a high prevalence of conditions such as asthma, diabetes
and hypertension.
Implications for the developing world
-------------------------------------
Such findings are likely to have growing relevance as the pandemic gains
ground in the developing world, where many millions of people live under
deprived conditions and have multiple health problems, with little access
to basic health care. As much current data about the pandemic come from
wealthy and middle-income countries, the situation in developing countries
will need to be very closely watched. The same virus that causes manageable
disruption in affluent countries could have a devastating impact in many
parts of the developing world.
Co-infection with HIV
---------------------
The 2009 influenza (H1N1) pandemic is the 1st to occur since the emergence
of HIV/AIDS. Early data from 2 countries suggest that people co-infected
with H1N1 2009 pandemic influenza virus and HIV are not at increased risk
of severe or fatal illness, provided these patients are receiving
antiretroviral therapy. In most of these patients, illness caused by H1N1
has been mild, with full recovery. If these preliminary findings are
confirmed, this will be reassuring news for countries where infection with
HIV is prevalent and treatment coverage with antiretroviral drugs is good.
On current estimates, around 33 million people are living with HIV/AIDS
worldwide. Of these, WHO estimates that around 4 million were receiving
antiretroviral therapy at the end of 2008.
Source: World Health Organization (WHO)
Global Alert and Response (GAR)
Pandemic (H1N1) 2009 Briefing note 9. [edited]
<http://www.who.int/csr/disease/swineflu/notes/h1n1_second_wave_20090828/en/index.html>
Preparing for the 2nd wave: lessons from current outbreaks Pandemic (H1N1)
2009
-------------------------------------------------------------------------------
Monitoring of outbreaks from different parts of the world provides
sufficient information to make some tentative conclusions about how the
influenza pandemic might evolve in the coming months. WHO is advising
countries in the northern hemisphere to prepare for a 2nd wave of pandemic
spread. Countries with tropical climates, where the pandemic virus arrived
later than elsewhere, also need to prepare for an increasing number of
cases. Countries in temperate parts of the southern hemisphere should
remain vigilant. As experience has shown, localized "hot spots" of
increasing transmission can continue to occur even when the pandemic has
peaked at the national level.
H1N1 now the dominant virus strain
----------------------------------
Evidence from multiple outbreak sites demonstrates that the H1N1 pandemic
2009 virus has rapidly established itself and is now the dominant influenza
strain in most parts of the world. The pandemic will persist in the coming
months as the virus continues to move through susceptible populations.
Close monitoring of viruses by a WHO network of laboratories shows that
viruses from all outbreaks remain virtually identical. Studies have
detected no signs that the virus has mutated to a more virulent or lethal form.
Likewise, the clinical picture of pandemic influenza is largely consistent
across all countries. The overwhelming majority of patients continue to
experience mild illness. Although the virus can cause very severe and fatal
illness, also in young and healthy people, the number of such cases remains
small.
Large populations susceptible to infection
------------------------------------------
While these trends are encouraging, large numbers of people in all
countries remain susceptible to infection. Even if the current pattern of
usually mild illness continues, the impact of the pandemic during the 2nd
wave could worsen as larger numbers of people become infected. Larger
numbers of severely ill patients requiring intensive care are likely to be
the most urgent burden on health services, creating pressures that could
overwhelm intensive care units and possibly disrupt the provision of care
for other diseases.
Monitoring for drug resistance
------------------------------
At present, only a handful of pandemic viruses resistant to oseltamivir
have been detected worldwide, despite the administration of many millions
of treatment courses of antiviral drugs. All of these cases have been
extensively investigated, and no instances of onward transmission of
drug-resistant virus have been documented to date. Intense monitoring
continues, also through the WHO network of laboratories.
Not the same as seasonal influenza
----------------------------------
Current evidence points to some important differences between patterns of
illness reported during the pandemic and those seen during seasonal
epidemics of influenza. The age groups affected by the pandemic are
generally younger. This is true for those most frequently infected, and
especially so for those experiencing severe or fatal illness. To date, most
severe cases and deaths have occurred in adults under the age of 50 years,
with deaths in the elderly comparatively rare. This age distribution is in
stark contrast with seasonal influenza, where around 90 percent of severe
and fatal cases occur in people 65 years of age or older.
Severe respiratory failure
--------------------------
Perhaps most significantly, clinicians from around the world are reporting
a very severe form of disease, also in young and otherwise healthy people,
which is rarely seen during seasonal influenza infections. In these
patients, the virus directly infects the lung, causing severe respiratory
failure. Saving these lives depends on highly specialized and demanding
care in intensive care units, usually with long and costly stays.
During the winter season in the southern hemisphere, several countries have
viewed the need for intensive care as the greatest burden on health
services. Some cities in these countries report that nearly 15 per cent of
hospitalized cases have required intensive care. Preparedness measures need
to anticipate this increased demand on intensive care units, which could be
overwhelmed by a sudden surge in the number of severe cases.
Vulnerable groups
-----------------
An increased risk during pregnancy is now consistently well-documented
across countries. This risk takes on added significance for a virus, like
this one, that preferentially infects younger people. Data continue to show
that certain medical conditions increase the risk of severe and fatal
illness. These include respiratory disease, notably asthma, cardiovascular
disease, diabetes and immunosuppression. When anticipating the impact of
the pandemic as more people become infected, health officials need to be
aware that many of these predisposing conditions have become much more
widespread in recent decades, thus increasing the pool of vulnerable people.
Obesity, which is frequently present in severe and fatal cases, is now a
global epidemic. WHO estimates that, worldwide, more than 230 million
people suffer from asthma, and more than 220 million people have diabetes.
Moreover, conditions such as asthma and diabetes are not usually considered
killer diseases, especially in children and young adults. Young deaths from
such conditions, precipitated by infection with the H1N1 virus, can be
another dimension of the pandemic's impact.
Higher risk of hospitalization and death
----------------------------------------
Several early studies show a higher risk of hospitalization and death among
certain subgroups, including minority groups and indigenous populations. In
some studies, the risk in these groups is 4 to 5 times higher than in the
general population. Although the reasons are not fully understood, possible
explanations include lower standards of living and poor overall health
status, including a high prevalence of conditions such as asthma, diabetes
and hypertension.
Implications for the developing world
-------------------------------------
Such findings are likely to have growing relevance as the pandemic gains
ground in the developing world, where many millions of people live under
deprived conditions and have multiple health problems, with little access
to basic health care. As much current data about the pandemic come from
wealthy and middle-income countries, the situation in developing countries
will need to be very closely watched. The same virus that causes manageable
disruption in affluent countries could have a devastating impact in many
parts of the developing world.
Co-infection with HIV
---------------------
The 2009 influenza (H1N1) pandemic is the 1st to occur since the emergence
of HIV/AIDS. Early data from 2 countries suggest that people co-infected
with H1N1 2009 pandemic influenza virus and HIV are not at increased risk
of severe or fatal illness, provided these patients are receiving
antiretroviral therapy. In most of these patients, illness caused by H1N1
has been mild, with full recovery. If these preliminary findings are
confirmed, this will be reassuring news for countries where infection with
HIV is prevalent and treatment coverage with antiretroviral drugs is good.
On current estimates, around 33 million people are living with HIV/AIDS
worldwide. Of these, WHO estimates that around 4 million were receiving
antiretroviral therapy at the end of 2008.
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