Hello
everyone,
I’d like to
thank you for taking a moment to view my new blog. I hope you’ll find it
enjoyable and informative! Also please leave a comment at the end if you have
any thoughts about the posting or would like to share any ideas!
A little about
myself, I am a Masters of Public Health student at the University of
Saskatchewan in Canada. I have a background in biology and nutrition with
working experience in the field of sports nutrition.
I’m starting
this blog to bring about public health topics of interest to the public, to
connect what I’m learning in class and applying it in a public setting. I think
this is extremely important as a public health professional to inform the
public and facilitate discussion on important topics pertaining to health.
My first
posting is going to be on a hot topic in the Canadian media, H5N1, or more
colloquially “bird flu”. If you weren’t already aware, the first reported death
in North America occurred just over a month ago in the Canadian province of
Alberta. A young woman in her late 20’s was travelling back to Canada from
China, where it is believed she contracted H5N1.1 Upon hearing about
this I decided to investigate a little more closely into what H5N1 is, if it is
serious, and should we be worrying about it.
What is H5N1?
As its
colloquial name suggests, H5N1 is a Highly Pathogenic Avian Influenza (HPAI)
type A of the subtype H5N1. H5N1 is unique as it is endemic in bird and poultry
populations across Asia and the Middle East and highly transmissible among bird
populations.2,3 (See Figure 1) First discovered in Hong Kong in 1997, it gained
national attention when 18 cases were identified resulting in 6 deaths.4
In 2003, a new genotype of the virus emerged (Z genotype) which has 2 distinct
clades, or strains, the first of which encompasses Cambodia, Laos, Malaysia,
Thailand, and Vietnam and the second found in China, Indonesia, Japan, and
South Korea.5 Fast forwarding to today, there have been as of
January 24, 2014, 650 confirmed cases of H5N1 in humans worldwide resulting in
386 deaths. (See Figure 2)6
 |
| Figure 1. - Map of H5N1 cases in birds and humans (http://www.news.ucdavis.edu/special_reports/avian_flu/images/avian_flu_map.gif) |
Is H5N1
serious?
The short
answer is yes it is. The case-fatality rate of persons who contract H5N1 is
approximately 60% (59.4% to be exact).4 Case-fatality rate is the
proportion of persons who contract and succumb to a disease in relation to the
total number of persons who contract the disease. On a scale of common flu
(<0.01%) to untreated rabies (~100%), a case-fatality rate of 60% is approximately
in line with Yersinia Pestis, the causative agent of the “Black Death”, which
plagued – pun intended – Europe in the middle ages.7 Now this number
is subject to much speculation as cases are confirmed in hospital settings
where they are likely to exhibit more severe forms of the disease.8
Since H5N1 is an influenza virus, initial symptoms are “flu-like” and many
people are unlikely to seek treatment until secondary symptoms such as
shortness of breath begin to set in.5, 9 Treatment for patients with
H5N1 includes the use of antiviral medications in combination with
corticosteroids and mechanical ventilation if necessary.5 The main
concern with H5N1 is whether it will “mutate” into a form which will cause
sustained human-to-human transmission. Currently, transmission of H5N1 occurs
mainly through direct contact with infected birds, eating improperly cooked
infected poultry, and fomites (surfaces contaminated with virus) arising from
infected bird droppings.3 “Mutation” of an influenza virus occurs
through 2 distinct pathways: antigenic drift, and antigenic shift. Antigenic
drift details small changes in the hemagglutinin and neuraminidase (The “H” and
“N” in H5N1) molecules, which results in creation of a new strain. This principle
underlies the need for an influenza vaccination every year. Antigenic shift is
a little more complex in that it only occurs when 2 completely different
influenza A viruses infect an animal host and combine to create a new virus
with completely different hemagglutinin and neuraminidase subtypes.10
For example the recent H1N1 pandemic (a worldwide outbreak of disease) in 2009 was the result of antigenic shift among influenza viruses
circulating in North American swine populations.11
 |
| Figure 2. - Worldwide distribution of H5N1 cases in humans (6) |
Should I be
worrying about it?
This is the
debate. The Public Health Agency of Canada (PHAC) has been quite adamant that
this appearance of H5N1 in North America is an isolated case and that we should
not be alarmed (see PHAC video below), while there are many people who are convinced that
this is the next great pandemic (see BBC documentary below). It is my belief that
H5N1 is not something for the public in North America to worry about for the
following reasons: it has exhibited no sustained human-to-human transmission,
there are worldwide monitoring efforts supported by international organizations
and foreign governments, vaccines have been approved for H5N1, and because of
previous international collaborative responses to pandemic threats.
Let me begin
with my last point. In 2003, North America was struck by a virus with certain
pathological similarities as H5N1.12 Most of you remember SARS (Severe
Acute Respiratory Syndrome) striking Toronto in 2003. While SARS is a
coronavirus and H5N1 is an influenza virus, they share many common symptoms
such as initial “flu-like” symptoms and lead to shortness of breath and
potentially viral pneumonia.13 One of the major differences between
H5N1 and SARS is that SARS is highly transmissible between humans. When SARS
set in in 2003, there were no vaccines available, there was little initial
collaboration between foreign governments and international organizations with
respect to disease reporting and data sharing,14 but governments and
agencies banded together in sharing information and quarantining cases to quell
the spread.15
In contrast,
H5N1 to date has not exhibited sustained human-to-human transmission, the key
factor of any pandemic. While there have been 2 suspected cases of
human-to-human transmission, they are very rare and are thought to have
occurred under extreme circumstances.2 Only if H5N1 mutates an
ability to sustain human-to-human transmission will it be a significant threat
to the human population. In addition, we are much better equipped today to
handle a potential H5N1 pandemic. H5N1 prophylactic (preventative) vaccines
have been approved and stockpiled in the event of a pandemic threat, and new vaccines against a pandemic strain can
be created in as little as 3 months.16 In addition, international
organizations such as the World Health Organization in collaboration with
foreign governments and public health agencies such as PHAC and the Centers for
Disease Control and Prevention (CDC) in the United States have led global
efforts in monitoring, transparency in reporting and data sharing of H5N1
cases, and the containment and control of infected bird and poultry populations
in order to prevent or mitigate a potential future H5N1 pandemic.17
In
conclusion, it is my opinion that the public fears about H5N1 in North America
should be put to rest while public health officials continue to monitor and
survey the virus under full public transparency.
References
4 - Ligon BL. Avian influenza virus H5N1: A review of its
history and information regarding its potential to cause the next pandemic.
Seminars in Pediatric Infectious Diseases 2005;16(4):326-335.
5 - The writing committee of the World Health Organization
Consultation on Human Influenza A/H5. Avian Influenza A (H5N1) Infection in
Humans. New England Journal of Medicine 2005 September 29, 2005(353):1374.
6 – World Health Organization. Cumulative number of
confirmed human cases for avian influenza
A (H5N1) reported to WHO, 2003-2014. 2014 January 24, 2014; http://www.who.int/entity/influenza/human_animal_interface/EN_GIP_20140124CumulativeNumberH5N1cases.pdf?ua=1.
A (H5N1) reported to WHO, 2003-2014. 2014 January 24, 2014; http://www.who.int/entity/influenza/human_animal_interface/EN_GIP_20140124CumulativeNumberH5N1cases.pdf?ua=1.
8 - Li FCK, Choi BCK, Sly T, Pak AWP. Finding the real
case-fatality rate of H5N1 avian influenza. J Epidemiol Community Health
2008;62(6):555-559.
10 – Battle CU. Essentials of public health biology: a guide
for the study of pathophysiology. Sudbury, Mass.: Jones and Bartlett
Publishers; 2009. p. 387-396.
11 - Smith GJD, Vijaykrishna D, Bahl J, Lycett SJ, Worobey
M, Pybus OG, et al. Origins and evolutionary genomics of the 2009 swine-origin
H1N1 influenza a epidemic. Nature 2009;459(7250):1122-1125.
12 - Gu J, Korteweg C. Pathology and pathogenesis of severe
acute respiratory syndrome. Am J Pathol 2007;170(4):1136-1147. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1829448/
15 - Chew S. SARS: how a global epidemic was stopped. WHO
Regional Office for the Western Pacific Region 2007 April 2007;85(4):324.http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2636331/
17 - USAID. Fact Sheet Avian Influenza Response:
Key Actions to Date. 2006 Feb 21, 2006; http://www.usaid.gov/sites/default/files/022206_avian.pdf
