- 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
- 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
- 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.
- Patricia A. Doyle DVM, PhD Bus Admin, Tropical Agricultural
Economics Univ of West Indies Please visit my "Emerging Diseases"
message board at: http://www.emergingdisease.org/phpbb/index.php Also my
new website: http://drpdoyle.tripod.com/ Zhan le Devlesa tai sastimasa
Go with God and in Good Health