Assessing the Severity of an Influenza Pandemic as of May 12, 2009

An influenza pandemic is caused by a virus that is either entirely new or has not circulated recently and widely in the human population, creating an almost universal vulnerability to infection. Although not all people ever become infected during a pandemic, nearly all people are susceptible to infection.  How contagious the virus is also influences the severity of a pandemic’s impact, as it can increase the number of people falling ill and needing care within a short time frame in a given geographical area. On the positive side, not all parts of the world, or all parts of a country, are affected at the same time.

One of the major determinant(s) of the severity of an influenza pandemic is the number of cases of severe illness and deaths that occur, which indicates the inherent disease potential of the virus. However, many other factors influence the overall severity of a pandemic’s impact.  A distinctive feature of influenza viruses is that mutations occur frequently and unpredictably in the eight gene segments, and especially in the so-called haemagglutinin gene, so the emergence of an inherently more virulent virus during the course of a pandemic can never be ruled out.

Different patterns of spread can also influence the severity of subsequent waves. For example, if schoolchildren are mainly affected in the first wave, the elderly can bear the brunt of illness during the second wave, with higher mortality seen because of the greater vulnerability of elderly people.

During the previous century, the 1918 pandemic began mild and returned, within six months, in a much more lethal form. The pandemic that began in 1957 started mild, and returned in a somewhat more severe form, though significantly less devastating than seen in 1918. The 1968 pandemic began relatively mild, with sporadic cases prior to the first wave, and remained mild in its second wave in most, but not all, countries.

Even a pandemic virus that initially causes mild symptoms in otherwise healthy people can be disruptive, especially under the conditions of today’s highly mobile and closely interdependent societies. Moreover, the same virus that causes mild illness in one country can result in much higher illness and death in another. In addition, the inherent virulence of the virus can change over time as the pandemic goes through subsequent waves of national and international spread.

Pandemics usually have a concentrated adverse impact in specific age groups. Concentrated illnesses and deaths in a young, economically productive age group will be more disruptive to societies and economies than when the very young or very old are most severely affected, as seen during epidemics of seasonal influenza.  Indeed, the overall vulnerability of the population can play a major role. For example, people with underlying chronic conditions (such as cardiovascular disease, hypertension, asthma, diabetes, among others) are more likely to experience severe or lethal infections. The prevalence of these conditions, combined with other factors such as nutritional status, can significantly influence the severity of a pandemic.

Finally, the quality of health services influences the impact of any pandemic. The same virus that causes only mild symptoms in countries with strong health systems can be devastating in other countries where health systems are weak, supplies of medicines, including antibiotics, are limited or frequently interrupted, and hospitals are crowded, poorly equipped, and understaffed.

Assessment of the current situation

To date, the following observations can be made, specifically about the H1N1 virus (swine flu), and more generally about the vulnerability of the world population. Observations specific to H1N1 are preliminary, based on limited data in only a few countries.

The H1N1 virus strain causing the current outbreaks is a new virus that has not been seen previously in either humans or animals. Although firm conclusions cannot be reached at present, scientists anticipate that pre-existing immunity to the virus will be low or non-existent, or largely confined to older population groups.

In addition, H1N1 appears to be more contagious than seasonal influenza.
With the exception of the outbreak in Mexico, which is still not fully understood, the H1N1 virus tends to cause very mild illness in otherwise healthy people. Outside Mexico, nearly all cases of illness, and all deaths, have been detected in people with underlying chronic conditions.

In the two largest and best documented outbreaks to date, in Mexico and the U.S., a younger age group has been affected than seen during seasonal epidemics of influenza. Though cases have been confirmed in all age groups, from infants to the elderly, the youth of patients with severe or lethal infections is a striking feature of these early outbreaks.

For several reasons, the prevalence of chronic diseases has risen dramatically since 1968, when the last pandemic of the previous century occurred. Today, the World Health Organization (WHO) estimates that 85% of the burden of chronic diseases is now concentrated in low- and middle-income countries. In these countries, chronic diseases show an earlier average age of onset than seen in more affluent parts of the world.

In these early days of the outbreaks, some scientists speculate that the full clinical spectrum of disease caused by H1N1 will not become apparent until the virus is more widespread. This, too, could alter the current disease picture, which is overwhelmingly mild outside Mexico.

Apart from the intrinsic mutability of influenza viruses, other factors could alter the severity of current disease patterns, though in completely unknowable ways, if the virus continues to spread.

Scientists are concerned about possible changes that could take place as the virus spreads to the southern hemisphere and encounters currently circulating human viruses as the normal influenza season in that hemisphere begins.

The fact that the H5N1 avian influenza virus is firmly established in poultry in some parts of the world is another cause for concern. No one can predict how the H5N1 virus will behave under the pressure of a pandemic. At present, H5N1 is an animal virus that does not spread easily to humans and only very rarely transmits directly from one person to another.

(Adapted from the CDC and the WHO)

SWINE FLU: PRECAUTIONS AND RECOMMENDATIONS

Update & Recommendations:  Swine Flu Outbreak (April 30, 2009)*

 

Swine Flu Update

As you may already know, human cases of swine influenza A (H1N1) virus
infection have been identified in several states and in other countries, primarily
Mexico.  So far in the U.S., 109  cases have been identified, and one  death has been reported.  In Mexico, according to current data from the
WHO (World Health Organization), 26 laboratory-confirmed cases have been
reported with 7 deaths.

According to the Centers for Disease Control & Prevention (CDC), this
influenza virus had previously been transmitted among swine, with no
human-to-human transmission.  However,
the virus has mutated, and human-to-human transmission of the virus is now
occurring and appears to be spreading, representing the threat of a pandemic. In
fact, the WHO  has upgraded the threat to
a phase 5 level, which is a “strong signal that a pandemic is imminent and that
the time to finalize the organization, communication, and implementation of the
planned mitigation measures is short.”  With
this in mind, it becomes prudent for churches and communities to take
precautionary measures to protect people and take advantage
of a narrow window of opportunity for intervention, hence the following
recommendations:

 

General Recommendations

(1)   
If you’re sick
or have symptoms that resemble the flu, stay home!
  Anyone who develops fever with either cough
or sore throat should be strongly encouraged to stay at home for seven days
after the onset of illness or at least 24 hours after symptoms subside,
whichever is longer. Persons who experience these symptoms and wish to seek
medical care should contact their health care providers to report illness before
seeking care at a clinic, physician’s office, or hospital. However, anyone who
has difficult breathing or shortness of breath or who is believed to be
seriously ill should seek immediate medical attention.

 

(2)   
When possible,
avoid contact with crowds
not only to protect yourself from becoming ill,
but also to protect others if you’re unknowingly incubating the virus.  This is especially important if your immune
system is compromised.

 

(3)   
 Cover your mouth and nose with a tissue if you’re
coughing or sneezing.

 

(4)    Wash your hands often!  Use either soap or one of the readily
available hand sanitizers to help protect you from viruses and other microbes.  (Hand sanitizers are inexpensive and readily
available in drugstores or supermarkets.) 
Hand washing is the single most effective way of preventing the spread
of not only the flu virus, but also other infectious agents.

 

(5)   
Avoid touching
your eyes, nose, or mouth.
 Microbes
are readily spread when one touches something that’s contaminated and then
touches one’s eyes, nose, or mouth.

 

(6)   
Practice good
health habits.
  Get plenty of sleep,
get exercise, manage your stress, drink plenty of fluids, and eat nutritious
food.  In other words, good health habits
can build up your resistance to germs.

 

Recommendations/considerations for
churches

            Have hand sanitizers
readily available (credence table, narthex, parish halls, etc.).

If you’re taking communion to someone in the
hospital, care facility, etc., be sure to use these sanitizers.

Consider receiving communion in one kind only (that
is, receiving only the host), instead of 
drinking directly from the chalice.

            Post signs in restrooms and
other public areas reminding people to practice good hygiene.

            Have qualified people
available for question-and-answer sessions.

For the time being, refrain from shaking hands
during the Peace because microbes are most easily passed from person to person
by touching.

 

Diocesan Emergency Preparedness Committee

 

 

*Adapted from CDC guidelines (www.cdc.gov/swineflu/).

Recent Advances in H5N1 Influenza Virus Research

RECENT ADVANCES IN H5N1 INFLUENZA VIRUS RESEARCH

Although the newspapers no longer carry headlines of the fears of a world-wide bird flu pandemic, the threat still remains. Public health officials make it very clear this virus can readily mutate into a virus ever bit as threatening in humans as it has become in birds. For example, India is in the midst of a significant outbreak in poultry and there is much concern by the health experts to keep the disease from spreading into Calcutta, a city of 14 million people. Of significance, a total of 14 countries have reported human infections, with Pakistan and Myanmar being the most recent in reporting their first infections. Moreover, it will be of extreme interest to observe the overall public health effects of the million or so homeless people devastated in Myanmar as a result of the recent cyclone.

To date, approximately 220 humans have died from the avian flu virus. All those who died had close contact with the virus from infected birds and/or fowl. However, the real concern is that the flu virus mutates quickly and the H5N1 virus is no exception. The threat is far from over.

Since the next influenza pandemic will very likely be caused by the H5N1 influenza virus, two recent articles in the March 2008 issue of the "Journal of Virology " indicate strong vaccine possibilities. The paper by Jiao et al reported on the single change substitution of an amino acid that appears to alter the virulence of the H5N1 virus. They demonstrated that serine 42 in the viral NS1 protein plays a critical role in the pathogenicity of H5N1 virus in mammalian hosts. These investigators believe their results provided strong evidence that the NS1 protein is a virulence factor for H5N1 influenza viruses and that multiple domains within NS1 may be targets for the development of a antiviral drugs and attenuated vaccines (J. Virol., 2008, 82:1146-1154).

In the second article, Watanabe and co-workers have been looking at the M2 protein that consists of three structural domains, one of which is a 54-amino acid cytoplasmic tail domain in the influenza A virus. In a previous study they demonstrated that deleting the M2 cytoplasmic tail caused a growth defect in the H1N1 influenza virus suggesting that the M2 cytoplasmic tail plays a vital role in virus replication. In their current study these investigators created an M2 tail mutant H5N1 virus, vaccinated mice with it, and challenged the mice with a lethal dose of H5N1 influenza virus. Their results showed that the mice were protected from death suggesting that the virus could not replicate and therefore be used as a vaccine ( J. Virol., 2008, 82: 2486 – 2492 ).

AVIAN INFLUENZA part 1

Deacon Bill (see below) has sent along this first column:

On both November 2 and 9, the Bishop of Arizona’s E-pistle included excerpts on pandemic influenza planning along with a partial list of additional resources. Since I have a relatively extensive background in the study of infectious diseases, I submit the following as an introduction on this potentially deadly infectious disease.

Infectious diseases are the leading cause of death worldwide. It is no secret that new and re-emerging microbial agents that can cause a number of infections, including influenza, are a growing concern among scientists. The Centers for Disease Control and Prevention (CDC) has reported that seasonal influenza causes more than 200,000 hospitalizations per year and about 36,000 deaths annually. Those at highest risk are the very young, the very old, those undergoing chemotherapy, or those whose immune systems are compromised, such as AIDS patients or organ transplant patients. Moreover, influenza can dramatically impact both our economy and all aspects of normal life.

Most virologists believe that another pandemic (worldwide) will occur. Indeed, influenza pandemics have occurred throughout history such as the 1918 Spanish flu outbreak. The major culprit responsible for ordinary influenza and all pandemics is the group A influenza virus, which includes the Avian (bird flu) influenza viruses. The major concern is that all these viruses are able to readily mutate. This is certainly true with the H5N1 Avian influenza virus, which is continuing to evolve. In 2006, there were about 100 confirmed cases of H5N1 in humans, the majority of them fatal. It is well known also that H5N1 virus continues to be a problem primarily among poultry in Asia and Europe. Although rare, person-to-person transmission has also been documented. What public health officials fear is that this virus may well mutate in ways that make sustained transmission of H5N1 possible. Even more troubling are the recent studies conducted at CDC that showed these viruses to be more lethal than the 1918 Spanish flu virus. This alone strongly implies a very potent disease-causing virus.

In another blog, I will discuss what a pandemic of Avian Influenza may look like.