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Flu News for Senior Citizens
Senior Citizens May be Safer Than Young Adults in
Flu Pandemic, Study Finds
1918 pandemic tended to kill the young, as has
recent bird flu
 March
1, 2007 - Evidence is mounting that senior citizens and the
elderly may not be the ones most in danger should there be an avian
influenza pandemic, contrary to what many have predicted, according to a new report
that looked at studies of the 1918 influenza pandemic. One of the great
unsolved mysteries surrounding this Spanish Flu pandemic is why it
tended to kill the young and healthy, rather than older people, say the
authors.
Unlike yearly influenza epidemics, in which death
rates are highest among infants, the elderly and those with chronic
health conditions, the 1918 influenza pandemic took its greatest toll on
healthy adults between the ages of 20 and 40.
One possible explanation, according to the article,
is supported by recent studies in mice with a reconstructed version of
the 1918 virus. The study found that an over-responsive immune system
may release a cytokine storm, or an excessive amount of immune system
proteins that trigger inflammation and harm the patient in the process.
It is also important to note that most deaths among
humans infected with the H5N1 avian influenza virus in recent years have
occurred in individuals under the age of 40. (See current cases, deaths
below this news report.)
The authors point out, however, it is not yet known
whether there is a higher percentage of young people in the affected
populations compared to older people, whether younger people are more
susceptible to infection or whether they have more exposure to infected
birds.
What is known is that there was a
lower-than-expected mortality among the elderly in the 1918 pandemic.
In this Journal of Infectious Diseases review
article now posted online, David M. Morens, M.D., and Anthony S. Fauci,
M.D., of the National Institute of Allergy and Infectious Diseases
(NIAID), part of the National Institutes of Health, conclude that
studies of the 1918 influenza pandemic, which killed some 50 to 100
million people around the globe, have so far raised more questions than
they answer.
Today, nearly a century after the 1918 influenza
pandemic, its mysteries remain largely unexplained, says Dr. Fauci,
NIAID director.
Much work remains to be done, by scientists as
well as by historians and other scholars, with regard to the many
unanswered questions surrounding this historic pandemic. These studies
must be part of our preparedness efforts as we face the prospect of a
future influenza pandemic.
In their article, Drs. Morens and Fauci review
several topics, including the origins of the 1918 pandemic influenza
virus, the excess mortality of the pandemic, the predilection to kill
the young and healthy, the lower-than-expected mortality among the
elderly, and the cyclicity of influenza pandemics over the past 100
years. Such topics are relevant today as highly pathogenic H5N1 avian
influenza viruses have spread from Asia to the Middle East, Europe and
Africa.
Highly pathogenic H5N1 influenza viruses have
primarily infected wild birds and domestic poultry populations in dozens
of countries, although at least 275 people have been infected and 167
have died.
As Morens and Fauci point out, the H1N1 virus that
caused the 1918 pandemic appears to be avian in origin, but the host
source of the 1918 virus has never been identified.
Furthermore, no major disease outbreaks among birds
were documented immediately before the 1918 pandemic. They suggest that
an avian influenza strain could have been hidden in an obscure
ecological niche, and the pandemic strain arose by the genetic
adaptation of that avian virus to a new human host.
The more we learn about influenza A viruses and
what they can do to maintain their deadly relationship with the human
species, the more remarkable they seem, says Morens. The challenge for
us is to learn as much about influenza viruses as they have already
learned about us.
The authors also discuss the high number of deaths
associated with the 1918 pandemic and the disease process, based on
clinical and autopsy studies published between 1918 and 1922.
Most pandemic deaths were associated with either an
aggressive bronchopneumonia, in which bacteria could be cultivated from
lung tissue at autopsy, or with a severe acute respiratory distress-like
syndrome (ARDS) characterized by blue-grey facial discoloration and
excessive fluid in the lungs.
In neither case is it known whether most deaths
were caused by a secondary bacterial infection or a primary viral
infection. They propose that the many excess deaths that occurred during
the 1918 influenza pandemic resulted from a disease process that began
with a severe acute viral infection that spread down the respiratory
tree causing severe tissue damage, which was often followed by secondary
bacterial invasion.
More definitive answers regarding the causes of
deaths due to the Spanish Flu may require a comprehensive
re-examination of the 1918 autopsy series, they note.
If a pandemic with similar characteristics were to
occur in the near future, Morens and Fauci predict that the relative
number of deaths would be substantially lower than that which occurred
in 1918.
In 2007 public health is much more advanced, with
better prevention knowledge, good influenza surveillance, more trained
personnel at all levels, well-established prevention programs featuring
annual vaccination with up-to-date influenza and pneumococcal vaccines,
and a national and international prevention infrastructure, they write.
In addition, two classes of antiviral drugs are
currently available, as well as antibiotics effective against bacteria
that cause influenza-associated pneumonia.
The most difficult challenge in mitigating the
effects of a severe pandemic today would be to ensure access to medical
care and resources, they note. Hospitals, medical personnel and drug
suppliers could be overwhelmed with huge demands for services, medicines
and vaccines, a situation that would be exacerbated in less developed
countries and impoverished regions.
Fauci and Morens conclude that the best hope for
the future lies in developing and stockpiling more broadly protective
influenza vaccines. In the meantime, prevention efforts should be
directed towards logistical planning, increased surveillance, the
development of medical countermeasures, an improved understanding of
pandemic risks, and an aggressive and broad research agenda.
Editor's Notes:
NIAID is a component of the National Institutes
of Health. NIAID supports basic and applied research to prevent,
diagnose and treat infectious diseases such as HIV/AIDS and other
sexually transmitted infections, influenza, tuberculosis, malaria and
illness from potential agents of bioterrorism. NIAID also supports
research on basic immunology, transplantation and immune-related
disorders, including autoimmune diseases, asthma and allergies. News
releases, fact sheets and other NIAID-related materials are available on
the NIAID Web site at
http://www.niaid.nih.gov.
The National Institutes of Health (NIH) The
Nation's Medical Research Agency includes 27 Institutes and Centers
and is a component of the U.S. Department of Health and Human Services.
It is the primary federal agency for conducting and supporting basic,
clinical and translational medical research, and it investigates the
causes, treatments, and cures for both common and rare diseases. For
more information about NIH and its programs, visit
www.nih.gov.
|
Cumulative Number of
Confirmed Human Cases of Avian Influenza A/(H5N1) Reported
to WHO
1 March 2007 |
|
Country
|
2003 |
2004 |
2005 |
2006 |
2007 |
Total |
|
cases |
deaths |
cases |
deaths |
cases |
deaths |
cases |
deaths |
cases |
deaths |
cases |
deaths |
| Azerbaijan |
0 |
0 |
0 |
0 |
0 |
0 |
8 |
5 |
0 |
0 |
8 |
5 |
| Cambodia |
0 |
0 |
0 |
0 |
4 |
4 |
2 |
2 |
0 |
0 |
6 |
6 |
| China |
1 |
1 |
0 |
0 |
8 |
5 |
13 |
8 |
1 |
0 |
23 |
14 |
| Djibouti |
0 |
0 |
0 |
0 |
0 |
0 |
1 |
0 |
0 |
0 |
1 |
0 |
| Egypt |
0 |
0 |
0 |
0 |
0 |
0 |
18 |
10 |
5 |
3 |
23 |
13 |
| Indonesia |
0 |
0 |
0 |
0 |
19 |
12 |
56 |
46 |
6 |
5 |
81 |
63 |
| Iraq |
0 |
0 |
0 |
0 |
0 |
0 |
3 |
2 |
0 |
0 |
3 |
2 |
| Lao People's
Democratic Republic |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
1 |
0 |
1 |
0 |
| Nigeria |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
1 |
1 |
1 |
1 |
| Thailand |
0 |
0 |
17 |
12 |
5 |
2 |
3 |
3 |
0 |
0 |
25 |
17 |
| Turkey |
0 |
0 |
0 |
0 |
0 |
0 |
12 |
4 |
0 |
0 |
12 |
4 |
| Viet Nam |
3 |
3 |
29 |
20 |
61 |
19 |
0 |
0 |
0 |
0 |
93 |
42 |
| Total |
4 |
4 |
46 |
32 |
97 |
42 |
116 |
80 |
14 |
9 |
277 |
167 |
|
Total number of cases includes number of
deaths.
WHO reports only laboratory-confirmed cases.
All dates refer to onset of illness. |
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