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
Sakshi Kapoor- Great work and provided a lot of information in a concise manner!!
ReplyDeleteQuestion - We know that preventative vaccine has been stockpiled and a new vaccine against the strain causing pandemic can be developed in 3 months so the question that arises is what would be the dose regimen for the vaccine of H5N1?
Hey Sakshi! Thank you for your insightful question. As for the dose regimen of a potential pandemic H5N1 vaccine we don't really know what it would be as these vaccines have not been created and tested yet. However, it is my knowledge that current H5N1 vaccines being stockpiled are a single shot prophylactic vaccine and thus to make an educated guess I would assume that a pandemic H5N1 vaccine would also be a single shot prophylactic vaccine. The dose regimen of a pandemic H5N1 vaccine would rely on how effective a single dose or multi-dose regimen is at creating sufficient antibody titers to H5N1 within the body. This could be a very important issue for vaccine manufacturers and public health organizations to look into because of the reliance on chicken eggs for the manufacturing of these vaccines, and since H5N1 is an avian flu, it might affect chicken populations and thus our abilities to create vaccines.
DeleteRupinder Kaur Brar- You did a great work for this blog.
ReplyDeleteQuestion-As,you mentioned that now we are well equipped to tackle any H5N1 Pandemic by prophylactic vaccines.But,You also mentioned that we are having a big threat from human to human transmitted pandemic,if it happens.(I have also read the reference you provided that says human to human transmission cases are occurring at rate of approximately 2 cases per cluster).So,my question is as we know that human to human transmission cases are increasing though at slower rate.What are the current preventative measures or strategies that are there to tackle this pandemic?If not,why being such a serious threat it has not been taken into account?
Thank You.
Hey Rupinder! Excellent question! While there have been documented human-to-human transmissions of H5N1, these have been very isolated and rare cases. Cases where there have been human-to-human transmission have occurred generally when a caretaker is in the same room as infected individual for many hours without any personal protective measures. Thus this is termed limited human-to-human transmission because it requires substantial close contact with an infected individual in order to transmit the disease, unlike the common flu which only requires you to touch a surface infected with influenza virus in order for you to contract the disease. Current efforts in preventing an H5N1 pandemic include: a faster and portable testing kit for H5N1 influenza, culling and killing off infected flocks of birds and poultry, and vaccinating poultry populations against H5N1. At a human level, cases identified with H5N1 are quarantined within hospitals until healthy or deceased. The most important effort so far in containing the spread of H5N1 across the globe has been data sharing and openness with regards to case reporting by governments and public health organizations worldwide in order to properly allocate resources, healthcare staff education, and antiviral medications to H5N1 endemic zones. Since public health organizations are on high alert with regards to H5N1, if/when a pandemic strain arises, the collective effort of governments and public health organizations will contain and control this disease in a manner similar to SARS in 2003.
DeleteHi Andrew, thank you for a great read. You mentioned that we shouldn't so worried about H5N1 because human-to-human transmission is low and we have pre-pandemic vaccines available. Now my worry is, we have no idea how effective these pre-pandemic vaccines will be during the onset of a pandemic and we won't know until the onset of a pandemic. By this time, thousands of people may die if we find that the vaccine is ineffective. What are your thoughts on this and what can we do to mitigate such a problem from occurring?
ReplyDeleteHi Jung-In! Wonderful question. I do agree that the current pre-pandemic schematic isn't ideal but it is unfortunately the best we have right now. The efficacy of converting these pre-pandemic vaccines into pandemic vaccines is estimated to take 3 months, which would include re-formulating, testing on primates, and then testing on humans for efficacy in producing a sufficient antibody titer. While you are right thousands of people may die in this time span, there is no guarantee that the conversion of pre-pandemic vaccines to pandemic vaccines will be 100% effective, and there is a concern with current influenza vaccine manufacturing techniques which use chicken eggs to "grow" the vaccine, the greatest effort we have going is global monitoring and global case-reporting of H5N1. Our one advantage in the containment of H5N1 is the shared responsibility in monitoring and reporting of H5N1 cases in humans and birds so we can stay one step ahead of the virus at all times. In terms of mitigating the loss of life while a pandemic-strain vaccine is created, we may need to look into new vaccine technologies. A TED talk by Mark Kendall out of Australia talks about re-thinking vaccines, and introduces a new technology which could be used to create and test a pandemic H5N1 vaccine in a shorter time frame than 3 months. This technology also shows promise in its ability to scale up vaccine production very quickly, cheaply, does not require a cold chain, and also does not require eggs (which an Avian Influenza might affect egg supplies). As seen in 2003 with the outbreak of SARS and in 2009 with the outbreak of H1N1, North America is poised and well prepared for an outbreak of H5N1 and with new technologies on the horizon, we will be even better prepared for the challenges ahead.
Delete