H1N1 Update: June 11, 2009

June 23, 2009

Novel H1N1 Influenza
Updated Key Points
June 11, 2009

• On June 11, 2009, the World Health Organization (WHO) raised the
worldwide pandemic alert level to Phase 6.
• Designation of this phase indicates that a global pandemic is
underway.
• There are now community level outbreaks ongoing in other parts of
the world.
• State and international borders don’t matter at this point. The bottom
line is that this new virus is among us all.
• While U.S. influenza surveillance systems indicate that overall flu
activity is decreasing in the United States, novel H1N1 outbreaks are
ongoing in different parts of the U.S., in some cases with intense
activity.
• In the United States, this virus has been spreading efficiently from
person-to-person since April and, as we have been saying for some
time, we do expect that we will see more cases, more hospitalizations
and more deaths from this virus.
• Because there is already widespread novel H1N1 disease in the United
States, the WHO Phase 6 declaration does not change what the United
States is currently doing to keep people healthy and protected from
the virus.
• Thus there is no change to CDC’s recommendations for individuals and
communities.
• WHO’s decision to raise the pandemic alert level to Phase 6 is a
reflection of epidemiological changes in other parts of the world and
not a reflection of any change in the novel H1N1 virus or associated
illness.
• At this time, most of the people who have become ill with novel H1N1
in the United States have not become seriously ill and have recovered
without hospitalization.
• In the United States, we have been preparing for this for some time.
• And we are actively and aggressively implementing our pandemic
response plan.
• Phase 6 is an indicator of spread and not of severity.

Novel H1N1 Influenza
Updated Key Points
June 11, 2009

• It’s uncertain at this time how serious or severe this novel H1N1
pandemic will be in terms of how many people infected have severe
complications or death related to novel H1N1 infection.
• There were three influenza pandemics in the last century and they
varied widely in severity.
• The 1918 pandemic killed tens of millions of people.
• The 1957 pandemic is thought to have resulted in at least 70,000
deaths in the United States.
• Deaths from the 1968-69 pandemic were about the same as for
seasonal influenza.
• This pandemic certainly poses the potential to be at least as serious as
seasonal flu, if not more so.
• Because this is a new virus, many people will not have immunity to it
and illness may be more severe and widespread as a result.
• We are still learning about this virus and expect that, like all influenza
viruses, it will continue to change.
• There are some encouraging signs:
o So far we have not seen an extensive pattern of very severe
illness related to this virus.
o Results of a serology study conducted by CDC suggest that
some adults may have some degree of preexisting crossreactive
antibody to the novel H1N1 flu virus, especially adults
older than 60.
o And, this virus does not have the genetic markers for virulence
that we saw in the 1918 pandemic virus, or that we see today in
the H5N1 virus in Asia that has been lethal among people.
• But it’s early days and too soon to predict what will happen.
• It is important to remember that the potential remains for the virus to
change and cause more severe disease.
• The real uncertainty is the fall and how the novel H1N1 virus will affect
the 2009-2010 influenza season in the United States.
• We are still learning about the severity and other epidemiological
characteristics of the novel H1N1 virus.
Novel H1N1 Influenza
Updated Key Points
June 11, 2009

• This information is important and will be taken into account when
making recommendations with regard to vaccine and other preventive
measures in the fall.
• CDC will update its guidance and recommendations as more
information about the novel H1N1 flu virus becomes available.
• It will be important that we continue to watch this virus carefully.
• The Southern Hemisphere is just going into their flu season and how
this virus behaves will give us some clues about what we can expect
for the Northern Hemisphere.
• The situation is indeed sobering, but it’s important to keep in mind
that we are not helpless.
We are taking action:
• The Federal Government is mounting an aggressive response to this
newly declared pandemic.
• CDC’s goals during this public health emergency are to reduce
transmission and illness severity, and provide information to assist
health care providers, public health officials and the public in
addressing the challenges posed by this newly identified influenza
virus.
• To this end, CDC continues to update guidance.
• Visit the CDC website at http://www.cdc.gov/h1n1flu/ for more
information or call 1-800-CDC-INFO.
• Everyday, we learn more about this virus and what we learn will
continue to inform the actions that we take in response.
• We are aggressively taking early steps in the vaccine manufacturing
process, working closely with manufacturing and the rest of the
government.
• Vaccines are a very important part of a response to pandemic
influenza.
• CDC isolated the new H1N1 virus, made a candidate vaccine virus, and
has provided this virus to industry so they can begin scaling up for
production of a vaccine, if necessary.
• There are many steps involved with producing a vaccine and we are
committed to going forward with the NIH, and FDA, BARDA, and the

Novel H1N1 Influenza
Updated Key Points
June 11, 2009

manufacturers of influenza vaccines, to see about developing full scale
vaccine production.
• Where possible, we are taking parallel steps to speed up the vaccine
process.
• If things go well, and we develop a full scale production, it would be
several months until the vaccine were available.
• So vaccine is an important tool for the future.
Public:
• So far, most people who have been ill with this virus have recovered.
• We are monitoring hospitalization and death rates.
• At this point, whether you are tested and actually diagnosed with
novel H1N1 is less important than what you do if you become sick.
• It’s possible that this summer, people around you may get sick and
you may get sick.
• Certainly in the fall, with our flu season, people around you will be
getting sick and you may get sick.
• Be prepared to stay home for a week or so if you are ill.
• Most people infected with this virus so far have experienced the
regular symptoms of flu (fever, cough, body aches + a significant
number of people have reported vomiting and diarrhea).
• For people who are critically ill, we do have antiviral medications in our
arsenal against flu.
• The priority use for influenza antiviral drugs at this time is to treat
severe influenza illness.
• Influenza antiviral drugs are prescription medicines (pills, liquid or an
inhaler) with activity against influenza viruses, including swine
influenza viruses.
• There are two influenza antiviral medications that are recommended
for use against swine influenza. These are oseltamivir (trade name
Tamiflu ® and zanamivir (Relenza ®).
• Influenza antiviral drugs work best when stated soon after illness
onset (within two 2 days), but treatment with antiviral drugs should
still be considered after 48 hours of symptom onset, particularly for
hospitalized patients or people at high risk for influenza-related
complications.
Novel H1N1 Influenza
Updated Key Points
June 11, 2009

• You have a role in protecting yourself and your family.
• Stay informed. Health officials will provide additional information as it
becomes available. Visit www.cdc.gov
• Everyone should take these everyday steps to protect your health and
lessen the spread of this new virus:
o Cover your nose and mouth with a tissue when you cough or
sneeze. Throw the tissue in the trash after you use it.
o Wash your hands often with soap and water, especially after you
cough or sneeze. Alcohol-based hand cleaners are also effective.
o Avoid touching your eyes, nose or mouth. Germs spread this
way.
o Try to avoid close contact with sick people.
o If you are sick with a flu-like illness, stay home for 7 days after
your symptoms begin or until you have been symptom-free for
24 hours, whichever is longer. This is to keep from infecting
others and spreading the virus further.
o Follow public health advice regarding school closures, avoiding
crowds and other social distancing measures.
o If you don’t have one yet, consider developing a family
emergency plan as a precaution.
Pandemic Severity, General
• Influenza pandemics can range in severity, mainly in terms of the
number of people that have severe illness and die.
• Pandemic severity may also change over time and will differ across
regions of the world, in different countries and even within different
communities within a country.
• Pandemic disease severity will vary depending on several factors: a
nation’s ability to provide health care to their people, the availability of
antiviral medications to treat those who are sick, differences in how
the disease affects people in different age groups, and the
effectiveness of efforts to reduce person-to-person transmission of
influenza.
• An evaluation of pandemic severity should be based on local
circumstances for this reason.
Novel H1N1 Influenza
Updated Key Points
June 11, 2009

• A pandemic severity index helps pubic health officials to match the
timing of the spread and severity of the outbreak with the appropriate
use of public health and community resources to minimize the number
of people who get sick and the number of people who die.
U.S. Pandemic Severity Index (PSI)
• CDC developed the U.S. Pandemic Severity Index (PSI) to describe the
severity of a pandemic in terms of illness and death.
• The U.S. PSI scale is based on the case-fatality ratio; the likelihood of
people dying from the disease.
• The PSI scale ranges from Category 1 to Category 5 and is comparable
to the U.S. hurricane severity index.
• Category 1 is the least severe and Category 5 is the most severe.
• At the current time, CDC estimates that the pandemic situation in the
U.S. would be equivalent to a pandemic severity index of 2. (This
would be most similar to the 1957 influenza pandemic, however, it’s
uncertain how the current situation will evolve over the coming
months so it’s not possible to make a predication about deaths at this
time.)
• CDC will re-evaluate the classification of the Pandemic Severity Index
should there be evidence that the pandemic has become more severe.
• The PSI will be adjusted based on that evaluation and appropriate
guidelines and recommendations provided.
• CDC emphasizes that unnecessary weight not be given to the numeric
categorization of the pandemic.
• According to the U.S. PSI:
o A category 1 pandemic has the following:
 Case fatality ratio of less than 0.1 percent
 Excess death rate of less than 30 per 100,000 people
 Illness rate of 20-40% of the population
 Less than 90,000 potential deaths (based on 2006 U.S.
population)
 Similar to a more severe seasonal flu year in the United
States
o A category 2 pandemic has the following:
Novel H1N1 Influenza
Updated Key Points
June 11, 2009
Page of 7 of 11
 Case fatality ratio of 0.1 percent to less than 0.5 percent.
 Between 90,000 and 450,000 deaths in the U.S. (based
on 2006 U.S. population)
 Excess death rate of between 30 to less than 150 per
100,000 people
 Illness rate of between 20 and 40 percent.
 Similar to 1957 pandemic.
o A category 5 pandemic has the following:
 Case fatality ratio of greater or equal to 2 percent
 Excess death rate of more than 600 per 100,000 people
 Illness rate of 20-40% of the population
 Greater than or equal to 1.8 million potential deaths
(based on 2006 U.S. population)
 Similar to the 1918 pandemic
• The importance of identifying a category of severity is only to help
guide the public health interventions recommended for individuals and
communities.
• The PSI scale helps public health officials match the range of public
health intervention efforts to the severity of a pandemic.
For a Category 1 to 3 pandemic:
 Ill adults and children are asked to stay home voluntarily.
 If someone in the household is sick, well adults and
children do not need to stay at home.
 School and child care dismissal is not generally
recommended, but may be considered depending on the
local impact of the disease.
 Workplace and Community adult social distancing efforts
(e.g., encouraging teleconferences instead of meetings,
reducing density, meaning the number of people crowded
into an enclosed space, in public transit and the
workplace, postponing or canceling selected public
gatherings, encouraging people to telework, or take
staggered shifts) are generally not recommended.
o For a Category 4 to 5 pandemic
Novel H1N1 Influenza
Updated Key Points
June 11, 2009

 Ill adults and children are asked to stay home voluntarily.
 If someone in the household is sick, well adults and
children should stay at home too.
 School and child care dismissal is recommended for up to
12 weeks.
 Workplace and Community adult social distancing efforts
(e.g., encouraging teleconferences instead of meetings,
reducing density, meaning the number of people crowded
into an enclosed space, in public transit and the
workplace, postponing or canceling selected public
gatherings, encouraging people to telework, or take
staggered shifts) are recommended
Declaration of Phase 6 and Travel
• At this time, CDC does not recommend against travel to any country.
• CDC will continue to monitor the H1N1 situation around the world and
will provide recommendations to U.S. travelers based on the changing
situation.
• Travelers should check the CDC travelers’ health website
(www.cdc.gov/travel) for information related to this outbreak, as well
as for health information on the prevention and management of flu.
• Travelers should also check the website of the embassy of the country
to which they are traveling for the latest updates on entry or exit
screening procedures which may impact their travel.
• CDC recommends that ill persons postpone travel both for their
protection and that of other travelers.
WHO Phases
• The World Health Organization (WHO) has developed a plan to be
prepared for a global outbreak of influenza to help countries to protect
the public’s health before and during a pandemic.
• This plan defines the “phases” of a pandemic which describe the global
risk for a pandemic and the extent of global spread.
• The WHO phases provide a benchmark to guide national preparedness
and planning for a pandemic, and helps to indicate when countries
should shift to response and mitigation efforts.
Novel H1N1 Influenza
Updated Key Points
June 11, 2009

• The WHO phases are:
o Phase 1: No new influenza virus subtypes have been detected in
humans. An influenza virus subtype that has caused human
infection may be present in animals. If present in animals, the risk
of human infection or disease is considered to be low.
o Phase 2: No new influenza virus subtypes have been detected in
humans. However, an animal influenza virus circulating among
domesticated or wild animals is known to have caused infection in
humans and poses a substantial risk of human disease.
o Phase 3: An animal or human-animal influenza reassortant virus
has caused sporadic cases or small clusters of disease in people,
but has not resulted in human-to-human transmission sufficient to
sustain community-level outbreaks. Human infection(s) that occur
with this new subtype occur with at most rare instances of humanto-
human spread, or spread to a close contact.
o Phase 4: Small cluster(s) of human infections with limited but
verified human-to-human transmission. The spread is highly
localized, suggesting that the virus is not well adapted to humans.
However, the virus has the potential to cause “community-level
outbreaks.
o Phase 5: There is human-to-human spread of the virus into at
least two countries in one WHO region. Most countries are not
affected but there are larger though localized cluster(s) of human
infections due to human-to-human spread. These changes suggest
that the virus is becoming increasingly better adapted to humans.
There is a substantial pandemic risk.
o Phase 6: The pandemic phase. There is increased and sustained
transmission with community level outbreaks in at least one other
country in a second WHO region. This phase indicates that a global
pandemic is under way.
WHO Phase 6 Declaration
• The World Health Organization (WHO) has declared Pandemic Phase 6;
that this outbreak of influenza is a pandemic, which means that the
current novel H1N1 flu which is spreading involves sustained humanto-
human transmission in two or more regions of the world.
• Because there is already widespread novel H1N1 flu virus disease in
the United States, the WHO Phase 6 declaration does not change what
Novel H1N1 Influenza
Updated Key Points
June 11, 2009

the United States is currently doing to keep people healthy and
protected from the virus.
• Thus there is no change to CDC’s recommendations for individuals and
communities.
• CDC’s initial recommendations were aimed at preventing and
minimizing illness and death in light of uncertainty about the how
severe novel H1N1 flu would be.
• It is important to remember that the potential remains for the virus to
change and cause more severe disease.
• CDC will update its guidance and recommendations as more
information about the novel H1N1 flu virus becomes available.
Significance of WHO Phase 6 Declaration – [Moderate] Severity
Index
• WHO has a three point scale to determine pandemic severity – mild,
moderate and severe.
• At this time, WHO has indicated this seems to be a moderately severe
pandemic.
• The WHO severity index advises countries about the possible impact
on health and other related issues as a result of the current novel
H1N1 flu outbreak.
• Similar to how on any given day the weather pattern and the severity
of weather will differ from country to country around the world and
even within a country, the novel H1N1 flu pandemic will affect
countries and communities in different ways.
• The effects of the novel H1N1 flu pandemic will not be the same for all
countries, and countries may not experience effects at the same time.
• Transmission of the novel H1N1 virus from person to person will affect
countries at different times of the year but also in different locations
within these countries.
• The potential health effects of the influenza pandemic will differ
depending on several factors: a nation’s ability to provide health care
to their people, the availability of antiviral medications to treat those
who are sick, differences in how the disease affects people in different
age groups, and the effectiveness of efforts to reduce person-toperson
transmission of influenza.
Novel H1N1 Influenza
Updated Key Points
June 11, 2009

• As understanding of the novel H1N1 virus becomes clearer over time,
the WHO recommendations may change. CDC will remain flexible in
order to respond in the best way possible to the changing situation and
provide updated guidance as more information becomes available.