NOTE:This page is not intended as a stand-alone Web document and is intended to serve merely as a Section 508-accessible version of the PowerPoint presentation "2009 H1N1: Overview of a Pandemic, April 2009 - August 2010."
2009 H1N1: Overview of a Pandemic
NOTE:This page is not intended as a stand-alone Web document and is intended to serve merely as a Section 508-accessible version of the PowerPoint presentation "2009 H1N1: Overview of a Pandemic, April 2009 - August 2010."
On a lavender background, this illustration provides a 3D graphical representation of a generic influenza virion’s ultrastructure, and is not specific to a seasonal, avian or 2009 H1N1 virus. A portion of the virion’s outer protein coat has been cut away, which reveals the virus’ contents, and a key has been included, which identifies these components.
The key depicts hemagluttinin, neuraminidase, M2 ion channels, and RNP.
A, B and C. Human influenza A and B viruses cause seasonal epidemics of disease almost every winter in the United States. The emergence of a new and very different influenza virus to infect people can cause an influenza pandemic. Influenza type C infections cause a mild respiratory illness and are not thought to cause epidemics. Influenza A viruses are divided into subtypes based on two proteins on the surface of the virus: the hemagglutinin (H), and the neuraminidase (N). There are 16 different hemagglutinin subtypes and 9 different neuraminidase subtypes. Influenza A viruses can be further broken down into different strains. Current subtypes of influenza A viruses found in people are influenza A (H1N1) and influenza A (H3N2) viruses. In the spring of 2009, a new influenza A (H1N1) virus emerged to cause illness in people. This virus was very different from regular human influenza A (H1N1) viruses and the new virus has caused an influenza pandemic.
Influenza B viruses are not divided into subtypes, however, influenza B viruses also can be further broken down into different strains.
Image of line drawn to represent the passage of time, with blocks of time depicted in different colors. The first block is resting on the line itself, the second block is a little above the line, the third block is highest above the line, the forth block is a little less above the line, and the fifth block is resting on the line. From left to right on the line, the first block of time is gray and labeled ‘Phases 1-3: Predominantly animal infections, few human infections’. From left to right on the line, the second block of time is orange and labeled ‘Phase 4: Sustained human to human transmission’. From left to right on the line, the third block of time on the line is red and labeled ‘Phases 5-6/Pandemic: Widespread human infection’ and is circled to emphasize the importance of Phases 5 and 6. From left to right on the line, the forth block on the line is blue and labeled ‘Post Peak: possibility of recurrent events’. From left to right on the line, the fifth block on the line is pale blue and labeled ‘Post Pandemic: disease activity at seasonal levels’.
Next we’ll describe what each phase means. In nature, influenza viruses circulate continuously among animals, especially birds. Even though such viruses might theoretically develop into pandemic viruses, in Phase 1 no viruses circulating among animals have been reported to cause infections in humans.
In Phase 2 an animal influenza virus circulating among domesticated or wild animals is known to have caused infection in humans, and is therefore considered a potential pandemic threat.
In 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. Limited human-to-human transmission may occur under some circumstances, for example, when there is close contact between an infected person and an unprotected caregiver. However, limited transmission under such restricted circumstances does not indicate that the virus has gained the level of transmissibility among humans necessary to cause a pandemic.
Phase 4 is characterized by verified human-to-human transmission of an animal or human-animal influenza reassortant virus able to cause “community-level outbreaks.” The ability to cause sustained disease outbreaks in a community marks a significant upwards shift in the risk for a pandemic. Any country that suspects or has verified such an event should urgently consult with WHO so that the situation can be jointly assessed and a decision made by the affected country if implementation of a rapid pandemic containment operation is warranted. Phase 4 indicates a significant increase in risk of a pandemic but does not necessarily mean that a pandemic is a forgone conclusion.
Phase 5 is characterized by human-to-human spread of the virus into at least two countries in one WHO region. While most countries will not be affected at this stage, the declaration of Phase 5 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.
Phase 6, the pandemic phase, is characterized by community level outbreaks in at least one other country in a different WHO region in addition to the criteria defined in Phase 5. Designation of this phase will indicate that a global pandemic is under way.
During the post-peak period, pandemic disease levels in most countries with adequate surveillance will have dropped below peak observed levels. The post-peak period signifies that pandemic activity appears to be decreasing; however, it is uncertain if additional waves will occur and countries will need to be prepared for a second wave. Previous pandemics have been characterized by waves of activity spread over months. Once the level of disease activity drops, a critical communications task will be to balance this information with the possibility of another wave. Pandemic waves can be separated by months and an immediate “at-ease” signal may be premature.
In the post-pandemic period, influenza disease activity will have returned to levels normally seen for seasonal influenza. It is expected that the pandemic virus will behave as a seasonal influenza A virus. At this stage, it is important to maintain surveillance and update pandemic preparedness and response plans accordingly. An intensive phase of recovery and evaluation may be required.
Chart showing CDC estimates of 2009 H1N1 Cases and Related Hospitalizations and Deaths from April 2009 to April 10, 2010, by age group. The full table is available at "https://www.cdc.gov/h1n1flu/estimates_2009_h1n1.htm#Table Cumulative".
This slide shows the characteristics of 2009 H1N1 from April 15, 2009 to April 10, 2010. In the background of the picture there is a large gray triangle, indicating that what is listed at the base of the slide, Cases, occurred in greater numbers than what is listed at the top of the slide, Deaths.
In between Deaths and Cases, Hospitalizations is listed in the middle of the slide. The slide shows in white lettering that a total of 61,000,000 cases occurred, a total of 274,000 hospitalizations occurred, and 12,470 deaths occurred. Along the edge of the slide, it says ‘Approximate Rate per 100,000 Population.’
At the bottom of the slide categories are listed: 0 to 4 years, 5 to 24 years, 25 to 49 years, 50 to 64 years,65 years and older. In the Cases section there is a bar chart with solid green bars above each age group that show in a general way, the relative number of cases there were for each age group. 5 to 24 years experienced the largest number of cases by far, with 0 to 4 years experiencing slightly fewer. 25 to 49 years experienced significantly fewer number of cases, but still more than 50 to 64 years and 65 years and older who were the next to lowest and lowest numbers respectively.
In the Hospitalizations section there is a bar chart with solid blue bars above each age group that show in a general way, the relative number of hospitalizations there were for each age group. 0 to 4 years experienced the largest number of hospitalizations by far, with the other groups appearing almost equal to each other. 5 to 24 years and 50 to 64 years both experienced a few more hospitalizations than did 25 to 49 years and 65 years and older.
In the Deaths section there is a bar chart with solid blue bars above each age group that show in a general way, the relative number of deaths there were for each age group. 0 to 4 years experienced the smallest number of deaths, with 5 to 24 years experiencing a few more, 25 to 49 years experiencing a few than 5 to 24 years, 50 to 64 experiencing a few more than 25 to 49 years, and 65 years and older experiencing about the same number as 25 to 49 years.
This slide shows the frequency of underlying conditions in adults who were hospitalized with 2009 H1N1, using EIP data from April 15, 2009 to February 16, 2010. A total of 4,987 hospitalizations were analyzed.
The slide is set up as a bar graph, with percentages listed on the Y axis and conditions listed on the X axis. For each condition, there are two percentages depicted, one in orange and one in green. In orange, the prevalence of the condition among adults hospitalized with 2009 H1N1 is indicated. In green, the prevalence of the condition among the general US population is indicated.
The conditions listed on the X axis along the bottom of the chart, going from left to right, are: Asthma, Diabetes, CVD, COPD, Neuro/Developmental, Neuromuscular Dis, Pregnant. For Asthma, the prevalence of the condition in the adult population hospitalized with 2009 H1N1 is 30 percent. For Asthma, the prevalence of the condition in the general adult populations is 7 percent. For Diabetes, the prevalence of the condition in the adult population hospitalized with 2009 H1N1 is 23 percent. For Diabetes, the prevalence of the condition in the general adult populations is 8 percent. For CVD, the prevalence of the condition in the adult population hospitalized with 2009 H1N1 is 20 percent. For CVD, the prevalence of the condition in the general adult populations is 7 percent. For COPD, the prevalence of the condition in the adult population hospitalized with 2009 H1N1 is 14 percent. For COPD, the prevalence of the condition in the general adult populations is 5 percent. For Neuro/Developmental, the prevalence of the condition in the adult population hospitalized with 2009 H1N1 is 7 percent. For Neuro/Developmental, the prevalence of the condition in the general adult population is 1 percent. For Neuromuscular, the prevalence of the condition in the adult population hospitalized with 2009 H1N1 is 1 percent. For Neuromuscular, the prevalence of the condition in the general adult populations is 0 percent. For Pregnant, the prevalence of the condition in the adult population hospitalized with 2009 H1N1 is 9 percent. For Pregnant, the prevalence of the condition in the general adult population is 1 percent.
This slide shows the frequency of underlying conditions among hospitalized patients and those who died from H1N1 compared to the general population. The slide is set up as a bar graph, with numbers listed on the Y axis and conditions listed on the X axis. For each condition, there are three estimates depicted, one in beige, one in blue, one in green. In beige, the prevalence of the condition among adults hospitalized with 2009 H1N1 is indicated. In blue, the prevalence of the condition among the people who died with H1N1. In green, the prevalence in the US general population.
The conditions listed on the X axis along the bottom of the chart, going from left to right, are: Asthma, COPD, Diabetes, Chronic CVD*, Morbid Obesity**, Neurocognitive Dis, Neuromuscular Dis, Pregnant.
For Asthma, the prevalence of the condition among adults hospitalized with 2009 H1N1 is 28. For Asthma, the prevalence of the condition among the people who died with 2009 H1N1 is 17. For Asthma, the prevalence of the condition in the US general population is 8.
For COPD, the prevalence of the condition among adults hospitalized with 2009 H1N1 is 8. For COPD, the prevalence of the condition among the people who died with 2009 H1N1 is 22. For COPD, the prevalence of the condition in the US general population is 4.
For Diabetes, the prevalence of the condition among adults hospitalized with 2009 H1N1 is 15. For Diabetes, the prevalence of the condition among the people who died with 2009 H1N1 is 19. For Diabetes, the prevalence of the condition in the US general population is 6.
For Chronic CVD*, the prevalence of the condition among adults hospitalized with 2009 H1N1 is 14. For Chronic CVD*, the prevalence of the condition among the people who died with 2009 H1N1 is 21. For Chronic CVD*, the prevalence of the condition in the US general population is 7.
For Morbid Obesity**, the prevalence of the condition among adults hospitalized with 2009 H1N1 is 16. For Morbid Obesity**, the prevalence of the condition among the people who died with 2009 H1N1 is 8. For Morbid Obesity**, the prevalence of the condition in the US general population is 5.
For Neurocognitive Dis, the prevalence of the condition among adults hospitalized with 2009 H1N1 is 7. For Neurocognitive Dis, the prevalence of the condition among the people who died with 2009 H1N1 is 11. For Neurocognitive Dis, the prevalence of the condition in the US general population is 0.
For Neuromuscular Dis, the prevalence of the condition among adults hospitalized with 2009 H1N1 is 7. For Neuromuscular Dis, the prevalence of the condition among the people who died with 2009 H1N1 is 8. For Neuromuscular Dis, the prevalence of the condition in the US general population is 0.
For Pregnant, the prevalence of the condition among adults hospitalized with 2009 H1N1 is 6. For Pregnant, the prevalence of the condition among the people who died with 2009 H1N1 is 6. For Pregnant, the prevalence of the condition in the US general population is 1.
This slide shows the 2009 H1N1 Cumulative Lab-Confirmed Death Rate, by Age Group from April 2009 through March 27, 2010. 2,689 deaths were analyzed. The slide is set up as a bar chart, with X and Y axes. On the Y axis it says ‘Deaths Per 100,000 Population’, and the Y axis starts at 0 at the bottom and goes up in .5 increments as follows: 0, 0.5, 1.0, 1.5, 2. On the X axis it lists age groups that go as follows from left to right: 0 to 4 years, 5 to 24 years, 25 to 49 years, 50 to 64 years, 65 years and older.
For 0 to 4 years, there were 0.51 deaths per 100,000 population. For 5 to 24 years, there were 0.52 deaths per 100,000 population. For 25 to 49 years, there were 1.11 deaths per 100,000 population. For 50 to 64 years, there were 1.87 deaths per 100,000 population. For adults 65 years and older, there were 1.10 deaths per 100,00 population.
Welcome! Thank you for visiting our website. With support from the Centers for Disease Control and Prevention (CDC), researchers at the Johns Hopkins School of Public Health developed an internet survey system to help monitor the safety of seasonal and H1N1 influenza vaccines across the United States. Our study was part of surveillance efforts launched by CDC to monitor influenza vaccine safety during the 2009/2010 influenza season.
Graphic showing General Information Tab on the CDC 2009 H1N1 web site H1N1 Flu and You, Caring for Someone Sick at Home, In the News, Antivirals/Flu Treatment, CDC Estimates of Cases, More >> Graphic showing Vaccination Tab on the CDC 2009 H1N1 web site General Information, For Clinicians/Healthcare Professionals, Vaccine Safety, Vaccine Supply Status, More>> Graphic showing Info for Specific Groups on the CDC 2009 H1N1 web site Health Care Providers, State, Local & Tribal Officials, Child Care Programs, People 65 and Older, People with Asthma, Parents and Caregivers, Pregnant Women, Traveling & Travel Industry More>>
Screenshot of a CDC flyer Everyday Preventive Actions That Can Help Fight Germs, Like Flu. Everyday Preventive Actions That Can Help Fight Germs, Like Flu CDC recommends a three-step approach to fighting the flu. CDC recommends a three-step approach to fighting influenza (flu). The first and most important step is to get a flu vaccination each year. But if you get the flu, there are prescription antiviral drugs that can treat your illness. Early treatment is especially important for the elderly, the very young, people with certain chronic health conditions, and pregnant women. Finally, everyday preventive actions may slow the spread of germs that cause respiratory (nose, throat, and lungs) illnesses, like flu. This flyer contains information about everyday preventive actions.How does the flu spread? Flu viruses are thought to spread mainly from person to person through the coughing, sneezing, or talking of someone with the flu. Flu viruses also may spread when people touch something with flu virus on it and then touch their mouth, eyes, or nose. Many other viruses spread these ways too. People infected with flu may be able to infect others beginning 1 day before symptoms develop and up to 5-7 days after becoming sick. That means you may be able to spread the flu to someone else before you know you are sick as well as while you are sick. Young children, those who are severely ill, and those who have severely weakened immune systems may be able to infect others for longer than 5-7 days.
What are everyday preventive actions? Everyday preventive actions are steps that people can take to help slow the spread of germs that cause respiratory illness, like flu. These include the following personal and community actions: Cover your nose and mouth with a tissue when you cough or sneeze. This will block the spread of droplets from your mouth or nose that could contain germs. Wash your hands often with soap and water. If soap and water are not available, use an alcohol-based hand rub. Avoid touching your eyes, nose, and mouth. Germs spread this way. Try to avoid close contact with sick people. If you or your child gets sick with a respiratory illness, like flu, limit contact with others as much as possible to help prevent spreading illness. Stay home (or keep your child home) for at least 24 hours after fever is gone except to seek medical care or for other necessities. Fever should be gone without the use of a fever-reducing medicine. If an outbreak of flu or another illness occurs, follow public health advice. This may include information about how to increase distance between people and other measures.
Screenshot of a CDC flyer CDC Says “Take 3” Steps to Fight the Flu Flu is a serious contagious disease. Each year in the United States on average more than 200,000 people are hospitalized and 36,000 people die from seasonal flu complications. This flu season there is a new influenza virus. This flu season there is a new and very different influenza virus causing illness called 2009 H1N1 flu. Flu is unpredictable but CDC expects flu to continue causing illness, hospitalizations, and deaths caused by either 2009 H1N! influenza or regular seasonal flu viruses. Flu-like symptoms include: fever cough sore throat runny or stuffy nose body aches headache chills fatigue some people may also have vomiting and diarrhea For more information visit www.cdc.gov/h1n1flu/ or www.flu.gov or call 800-CDC-INFO. Department of Health and Human Services Centers for Disease Control and Prevention January 13, 2010
Screenshot of a CDC flyer Seasonal and 2009 H1N1 Flu: A Guide for Parents And they work best when started during the first 2 days of illness. These drugs can be given to children. What should I use for hand cleaning? Washing hands with soap and running water (for as long as it takes to sing the “Happy Birthday” song twice) will help protect against many germs. If soap and water are not availalable, use an alcohol-based rub. If your child is sick What can I do if my child gets sick? Talk to your doctor early if you are worried about your child If your child is 5 years or older and otherwise healthy and gets flu-like symptoms, including a fever and/or cough, consult your doctor as needed and make sure your child gets plenty of rest and drinks enough fluids. If your child is younger than 5 (and especially younger than 2) or of any age and has a medical condition (like asthma, a neurological condition, or diabetes), and develops flu-like symptoms, call a doctor to see if your child should be examined. This is because younger children and children who have chronic medical conditions are at higher risk of serious complications from flu infection, including 2009 H1N1 flu. What if my child seems very sick? Even children who have always been healthy before or had the flu before can get a severe case of flu. Call for emergency care or take your child to a doctor right away if your child of any age has any of the warning or emergency signs including: Fast breathing or trouble breathing Bluish or gray skin color Not drinking enough fluids (not going to the bathroom or making as much urine as they normally do) Severe or persistent vomiting Not waking up or not interacting Being so irritable that the child does not want to be held Flu-like symptoms improve but then return with fever and worse cough Has other conditions (like heart or lung disease, diabetes, or asthma) and develops flu symptoms, including a fever and or/cough Can my child go to school, day care or camp if he or she is sick? No. Your child should stay home to rest and to avoid giving the flu to other children When can my child go back to school after having the flu? Keep your child home from school, day care or camp for at least 24 hours after their fever is gone (Fever should be gone without the use of fever-reducing medicines) A fever is defined as 100 degrees F or 37.8 degrees C. Fpr more information, visit www.cdc.gov or www.flu.gov or call 800-CDc-INFO
Get email updates
To receive weekly email updates about this site, enter your email address:
Contact Us:
- Centers for Disease Control and Prevention
1600 Clifton Rd
Atlanta, GA 30333 - 800-CDC-INFO
(800-232-4636)
TTY: (888) 232-6348 - Contact CDC-INFO