| PRESS RELEASE: August 27, 2006
Avian
Influenza: The Next Pandemic?
In recent
decades, Americans have been subjected to various news reports
warning of potential threats to public health due to the emergence of a new “killer
flu”. These illnesses always seem to have exotic names and appear to affect
only foreign people in distant and far off lands. Through the years we’ve
watched as reports of
Hong Kong
flu, Swine flu,
West Nile
virus and SARS have flashed across our television screens. Americans viewed
with collective horror the epidemiological effects of the dreaded Ebola virus as
its story was played to light by
Hollywood
movie actors in the 1995 thriller “Outbreak”. While these diseases can be
devastating, they are typically limited in their spread to either localized
regions or certain at risk populations. This is not in a small part due to the
prudent reactions of local, national and international healthcare officials who
have taken the situations at hand and implemented precautionary health measures
to the benefit of all. Source: Centers for Disease Control
What
is it, then, that makes Avian Influenza, not even circulating among humans, so
different from other potential epidemics? What would prompt entire countries to
close their borders to effected countries, like several countries have, or cause
the deaths of over 200 million birds due to disease or culling to prevent the
disease? What would cause
President George Bush to approach Congress with a 7.1 billion dollar plan to
prepare for possible outbreaks of an epidemic that doesn’t
even exist in a human-to-human mode? There are currently no reports of any
humans who have contracted the disease other than direct contact with infected
birds. And scientists have known about this H5N1 strain for eight years. Why all
the publicity now? The answer may best be explained by analyzing the nature and
evolution of the familiar seasonal influenza virus, or what we know as the
common flu.
Seasonal Influenza - A Flu Primer. Each year most Americans are
content in taking routine precautions against garden variety flu strains which
plague us during flu season, one which often begins in October and ends as late
as April. This time of year thousands of us stock up on supplies of vitamins and
flu medicines, try to exercise, eat well and get plenty of rest to support our
immune systems, and otherwise make ready for the inevitable spread of “the bug”.
And each season despite our best efforts, anywhere from five to twenty
percent of the population will eventually succumb to the achy, feverish,
laying-in-bed-with-chills type experience of uncomplicated influenza. In spite
of their best efforts, over 200,000 Americans are hospitalized each year from
the illness and over 36,000 will die from the disease, mostly from complications
like pneumonia, striking mainly elderly individuals and those with underlying
health conditions.
Flu
symptoms are caused by viruses that infect the respiratory tract. Two main types
of influenza viruses -- influenza type A and influenza type B -- cause the
outbreaks and epidemics of respiratory illness that occur almost every winter.
Types A and B are constantly changing, each with numerous subtypes reoccurring
regularly. Hence the reason we need to get our flu shots updated each year.
 The
influenza virus is spread from person to person primarily through coughing and
sneezing. Less often, it is spread by touching a surface that has live virus on
it, like shaking a hand or touching a phone or faucet handle contaminated with
the virus, then touching the nose, mouth or eyes. Droplets of infected airborne
pathogens are breathed in and the virus is passed through the nasal passages,
throat, bronchial tubes, and lungs.
The typical incubation period is one to four days, (two being the average).
Symptoms of the common flu can be quite abrupt, often beginning with fever
lasting a day or two. Somewhere between day 2 and day 4 of the illness, the
achiness subsides and respiratory symptoms begin to increase. Since influenza is
a virus, it can’t be treated with antibiotics.The virus can settle anywhere
in the respiratory tract, producing symptoms of a cold, croup, sore throat,
bronchitis, sinus or ear infections, or pneumonia. Nasal discharge (runny nose)
and sneezing are common.
Type A
Influenza
Source: Centers
for Disease Control
These symptoms (except the cough) usually disappear within 4-7 days. Sometimes,
the fever returns. Cough and tiredness can last for weeks after the rest of the
illness is over. Doctors can perform tests to see if you have the flu if you are
in the first few days of your illness.
Influenza
viruses are highly contagious and adults are typically infectious one to five
days from onset. Children can shed virus for several days and can remain
infectious for over ten days beyond, while severely immunocompromised persons
can shed the virus for weeks or months. Because the flu is airborne, is highly
communicable and has a short incubation period, it often strikes a community all
at once, creating a cluster of school or work absences. That’s why within 2 or
3 weeks of its arrival in a school, much of the classroom has had it.
Quick Change Artist: Influenza’s Antigenic Drift & Shift. Influenza
has been described by science as the classic emerging and reemerging infectious
disease. That’s because the virus replicates as it enters a host cell then
infects by reproducing its own genetic material, using the host cell’s
resources to produce hundreds of copies of its own hereditary matter, or
Ribonucleic Acid (RNA). In this way, the virus takes over the cell's
productivity. Now, instead of producing only new cellular material, the cell
produces hundreds of new virus particles; ones which are eventually released
from the cell and drift off in search of their own host cell to pirate.
 If
the virus would make a perfect copy of itself as it reproduced, there’d be no
problem for science to determine the RNA and manufacture a potent vaccine.
However, influenza viruses are constantly making small and permanent mutations
as they replicate, a process known as “antigenic drift”. This can produce
new strains that may not be recognized by the body’s immune system and can
even cause re-infection.
Hence
the reason you need a new flu vaccine every year, and the reason that despite a
vaccination, you can still come down with the flu. Each year, the flu vaccine
companies make their best estimate as to which strains already circulating will
be the ones that will predominant during the flu season.
Human
beings are not the only species susceptible to influenza. Birds, dogs, pigs,
horses, seals - even tigers and whales - are among the animals prone to
infections from influenza. And normally, animal viruses do not infect humans.
But what would happen if there were a more abrupt mutation in a Type A
influenza virus, known as “antigenic shift”, which would allow genetic
materials from two different animal species to swap or re-assort? The result
would be a novel, never-before-seen subtype from both parent viruses. One to
which no person alive today has a pre-existing immunological protection against.
According to the World Health Organization, pandemics arise when such a
novel influenza virus emerges, infects humans, and spreads efficiently and
sustainably among them. This type of mutation is a rare but recurrent event,
occurring naturally two to three times a century. Once such an event starts and
reaches a certain level of local or regional spread, continued worldwide spread
is considered inevitable Influenza pandemics (worldwide epidemics) have been
responsible for the deaths of millions of people throughout history.
Avian Influenza. Usually, “avian influenza virus” refers to
influenza A viruses found chiefly in birds.
Migratory waterfowl – most notably wild ducks – are the natural
reservoir of all fifteen subtypes of influenza viruses known to infect birds.
They are also the most resistant to infection. Contact with wild migratory
waterfowl, whether indirect or direct, has been implicated as a frequent cause
of epidemics in domestic flocks.
Avian
influenza viruses can be classified into two forms: "low pathogenic"
and "highly pathogenic" - based on the severity of the illness they
cause in poultry. The low pathogenic form usually causes only mild symptoms
(such as ruffled feathers and a drop in egg production) and may even go
undetected. However, the highly pathogenic form spreads more rapidly through
flocks of poultry.
Among
birds, this form may cause disease that affects multiple internal organs and has
a mortality rate that can reach 90-100%, often within 48 hours. Influenza
viruses of the highly pathogenic form are caused by viruses of the subtype H5 or
H7.
Domestic
poultry, including chickens and turkeys, are particularly susceptible to
epidemics of rapidly fatal influenza. Apart from being highly contagious, avian
influenza viruses are readily transmitted from farm to farm by mechanical means,
such as contaminated equipment, vehicles, feed, cages, or clothing. Infected
birds shed flu virus in their saliva, nasal secretions and feces. These highly
pathogenic viruses can survive for long periods in the environment, especially
when temperatures are low.
Colorized
Transmission Electron Micrograph of Avian Influenza A H5N1
Viruses Grown in MDCK Cells The viruses are gold, and the MDCK cells
are green. (Photo: CDC/C. Goldsmith, J. Katz, and S. Zaki)
Subtype H5N1 – A Novel Mutation. In
1997 epidemiologists and public health officials from around the world got their
first glimpse of an entirely new variety of influenza which caused the deaths of
six people in
Hong Kong
. Known simply as subtype H5N1 for the surface proteins which the virus carries,
the new strain had only ever previously been observed in birds.
This
was the first documented case of an influenza virus jumping directly from
chickens to people. Public health authorities responded by ordering the
slaughter of more than 1.4 million live poultry – every duck, goose and
chicken in Hong Kong - to prevent further spread to humans.
Since then, the H5N1 strain of the bird flu has slowly spread through bird
populations in
Asia
,
Europe
and now parts of the
Middle East
and
Africa
causing the largest and most severe outbreaks in poultry on record. With its
spread, there have been over 169 confirmed cases of H5N1 virus in humans from
seven different countries (
Vietnam
,
Thailand
,
Indonesia
,
China
,
Cambodia
, and within the past two months,
Turkey
and
Iraq
). Over half of these victims have died (53%). In most instances, the influenza
struck people who had direct or close contact with infected poultry or
contaminated surfaces; however, in a few instances human-to-human spread of H5N1
has occurred.
Samples
obtained from the most recent victims in
Turkey
analyzed at the National Institute of Medical Research in
London
show that H5N1 has undergone a slight mutation which makes it more likely to
attach to human cells as well as chicken cells. Latest cases in northern
Iraq
have officials concerned that the virus may also now be spreading undetected
among domestic fowl, as there were no confirmed reports of sick birds before the
human cases.
In
chickens, H5N1 seems to spread to all internal organs, but in humans it appears
to devastate the lungs in particular. Researchers at the
University
of
Hong Kong
have found that a victim’s own immune system may be part of the problem. It
reacts to the virus with a flood of chemical messengers that draw white-blood
cells into the lungs, where they trigger a massive inflammatory reaction. This
may explain why most of the disease fatalities were previously healthy children
or young adults.
To
date, H5N1 viruses have not been associated with the type of community-wide
outbreaks that are characteristic of human influenza. Among scientists who feel
a pandemic is inevitable is Dr. Jai P. Narain, Director of WHO's communicable
diseases department, who states "We may be at almost the last stage before
the pandemic virus may emerge. Whether the avian influenza pandemic will occur,
that is not the question any more, [but] as to when the pandemic will
occur."
Experts
fear the virus, which mostly affects birds, could mutate to a form that can be
easily transmitted between people — sparking a pandemic that could kill
millions. Theoretically, many different avian influenza viruses have the
potential to evolve into a pandemic virus. But H5N1 is of particular concern for
several reasons. First, the subtype has already inherited several ugly
characteristics that make it quite similar to a virus that triggered the worst
influenza pandemic in human history which occurred early last century.
 Known
as the Spanish Flu, the virus struck in late winter 1918; it quickly spread
around the globe, infecting nearly one third of the world’s population with a
mortality rate of 2.5%, and killed 20 to 40 million people by the spring of
1919. Only
American Samoa
and parts of
Iceland
were spared an outbreak.
Although this
pandemic was considered exceptional, in October 2005, two teams of scientists
were able to determine that four of the eight genes in the H5N1 strain contain
mutations seen in the deadly Spanish flu virus 88 years ago.
The
researchers analyzed autopsy tissue from US Army soldiers who died from the flu
in 1918, and removed lung tissue from the frozen body of an exhumed flu victim
from an Alaskan village wherein 85 percent of the adult population died in just
five days and were buried in the ice the same year.
Analysis of all eight genes showed the Spanish flu came directly from a bird
virus and moved into humans after
slowly mutating. The H5N1 has adapted itself to jump
from birds to people in at least 169 documented cases.
1918: Flu victims crowd into an emergency hospital in Kansas
National Museum of Health &
Medicine
Historic Chart Showing Mortality Rates in
America
and
Europe
during 1918 and 1919
(Photo: Image “Reeve
3143,”
National
Museum
of Health and Medicine, Armed Forces
Institute
of
Pathology
,
Washington
,
D.C.
)
Second, H5N1 is particularly
virulent, killing close to 100 percent of susceptible birds and more than half
the people who have been infected. The virus appears to be spreading, including
most recently from
Asia
to
Europe
to the
Middle East
and now to
Africa
; it has killed tens of millions of birds in the countries it infects. Although
the bird flu virus is extremely deadly to humans, it's likely that it would
become less virulent if it adapted for human-to-human spread. But no will no for
certain until it does.
Third, H5N1 mutates rapidly
and has a documented propensity to acquire genes from viruses infecting other
animal species. It seems to be affecting more and more species, including cats,
which usually aren't susceptible to bird flu, and pigs, which traditionally have
been a species that acts as a "mixing bowl" for viruses transmitted
between birds and people.
Pandemic Planning. Experts
from around the world are watching the H5N1 situation very closely and are
preparing for the possibility that the virus may begin to spread more easily and
widely from person to person. While neither the timing nor the severity of the
next pandemic can be predicted, evidence that the virus is now endemic in bird
populations means that the present level of risk will not be easily diminished.
In a recent statement, Dr. David Nabarro, who heads the UN drive to contain the
virus admits, "Every 30 years, we do get massive pandemics of human
influenza. It's likely that the next pandemic will be caused by a version of
bird flu."
Theoretically,
the H5N1 bird flu virus could become a pandemic flu virus overnight. Per Nabarro,
only two more mutations are needed for it to become easily transmissible among
humans. These mutations could occur either at random or if the virus mixes its
DNA
with a human flu virus inside a pig or a human. “"I wake up every
morning thinking that today could be the day that I will see a report about a
strange case of bird flu among humans." Nabarro has been warning
governments around the world to prepare for a pandemic “…as if it were going
to start tomorrow.”
According to the World Health Organization (WHO), once a fully
contagious virus emerges, its global spread is considered inevitable, especially
if it coincides with a seasonal outbreak of influenza. The WHO lists six stages
leading from the detection of a new flu virus in animals to a global human flu
pandemic. So far, the H5N1 bird flu has been at stage 4: small, highly localized
clusters of human infections. At this stage, the virus cannot spread easily from
person to person. The plan for containment involves a rapid deployment of
epidemiologists and trained medical investigators to the scene of the first
reports of the virus spreading between humans, and the use of anti-virals and
antibiotics. Quarantine would be part of the plan.
The WHO believes a new strain will probably emerge in a rural area
and spread from its first human victim into a family and a community. Past
pandemics have spread globally in two and sometimes three waves. Not all parts
of the world or a single country are expected to be severely affected at the
same time. Countries might, through measures such as border closures and travel
restrictions, delay arrival of the virus, but cannot stop it. The pandemics of
the previous century encircled the globe in 6 to 9 months, even when most
international travel was by ship. With the speed and volume of international air
travel today, experts fear the virus could spread more rapidly, possibly
reaching all continents in less than 3 months.
Should Floridians be concerned? Since there have been no cases of
the H5N1 virus anywhere in the
United States
, the current risk for outbreak is low.
Florida
has a very strong and robust surveillance system on the alert to potential bird
flu, including the use of “sentinel physicians” assigned to report any
unusual occurrences of avian flu to the CDC and to the Florida Department of
Health. The CDC has increased its personnel at the Miami Quarantine Station to
provide services to the international ports of entry in
Florida
. And while there is no commercially available vaccine to protect humans against
the H5N1 virus that is being seen in
Asia
,
Europe
, parts of the
Middle East
and
Africa
, development efforts are currently taking place. The state has tested its
ability to provide mass inoculations should the need arise, and those tests have
been very successful.
The Florida Department of Agriculture and Consumer Services and The Fish and
Wildlife Conservation Commission have been working together to provide bird
surveillance services both in domestic poultry and in the wild. On a national
level, the
US
is currently stockpiling anti-viral medications and in
Atlanta, the CDC recently published an 18 page pandemic planning guide (January 2006)
for individuals and families in anticipation of a global pandemic which may be
helpful to you and your family in the event of a pandemic. For copies of this
article visit our website at http://www.MyMDNow.com.
Dr. Peter Lamelas is Residency trained in Internal Medicine and Board Certified
in Emergency Medicine (ABPS). He was Medical Director of the Emergency
Department of Columbia Hospital in
West Palm Beach
for 17 years and is a long standing
member of the
American
College
of Emergency Physicians. In 2001,
he received a gubernatorial appointment to serve on the State of
Florida
’s Board of Medicine. In 1993 he
earned his Masters Degree in Business Administration from
Nova
Southeastern
University
, and on
February 5, 2005
realized a long term dream of building, owning and operating his own highest
quality urgent care center in suburban
Lake Worth
,
Florida
.
|
