Davey, Victoria J. MPH, RN
“Influenza killed more people in a year than the Black Death of the Middle Ages killed in a century; it killed more people in twenty-four weeks than AIDS has killed in twenty-four years.” So writes John M. Barry in his bestselling account of the horrific “Spanish flu” pandemic of 1918–20, The Great Influenza.1 Today, such knowledge of history is guiding disaster planners as they consider equally staggering scenarios among their forecasts for an influenza pandemic (see Table 1, page 52).
The prospect of an influenza pandemic caused by a lethal viral subtype is of great concern to nurses, who understand the impact such an event could have, and it poses unaccustomed challenges to disaster planners. The typical model for responding to local disasters such as floods or hurricanes—in which communities provide support to a stricken area and immediate aid is expected from regional, state, or national entities—could be greatly curtailed in a pandemic because of its potentially global scope. And the weeks- or months-long duration of a pandemic could result in the exhaustion of essential personnel and supplies that would need repeated replenishing. But because a pandemic makes every community vulnerable, little outside help might be available to those coping with mass illness and death. Communities not yet affected would undoubtedly feel the need to reserve resources to protect themselves against the threat, while those recovering would be too overwhelmed and depleted to assist.
On the other hand, a pandemic with a nonvirulent strain could be a very manageable event. Overreacting to a disease outbreak (by unnecessarily closing schools or limiting travel, for example) can also cause harm. The challenge in pandemic influenza planning is to find a balance between risk and preparedness that realistically estimates the consequences of a pandemic and doesn't rob resources from the many everyday health care and social challenges. Planners should be aware of preparations being made at local, state, and federal levels; proceed logically with their own planning; and be able to interpret evidence that indicates an influenza pandemic is unfolding. Also, it should be noted, every month that goes by without an outbreak is an opportunity to stockpile antiviral drugs and protective equipment and to develop plans for continuing to deliver health care and essential services in the event of a pandemic outbreak.
SEASONAL or PANDEMIC INFLUENZA?
Influenza outbreaks occur every year. Called seasonal, or interpandemic, influenza, the illness is caused by viral strains that have circulated in humans previously (thus, some people are immune) and for which there are effective vaccines. Most people experience seasonal influenza as a miserable week of fever, fatigue, aching muscles, and hacking cough. Yet in the United States, more than 200,000 excess hospitalizations and perhaps 40,000 deaths occur annually from complications of influenza, mostly among the very young and old.2, 3
The predominant mode of influenza transmission is probably virus-containing respiratory droplets (larger than 10 microns in diameter). An infected person releases droplets when sneezing, coughing, or speaking, and a nearby person then inhales them into the respiratory tract, or the virus is deposited on mucous membranes such as the eyes, nose, or mouth. Transmission may also occur via inhalation of smaller airborne viral particles (smaller than 5 microns in diameter) that can remain suspended in the air for minutes to hours, or by picking up virus from surfaces like countertops and then touching the mucous membranes.4, 5 Efficient transmission is characteristic of influenza: infected people may shed virus for half a day before they feel symptoms. Influenza's brief incubation period (the time between infection and the development of symptoms) averages just two days. The virus's reproduction ratio (the number of persons infected by one source person) depends on the strain and subtype, the quantity and type of contacts among people, and the susceptibility of the uninfected person. An infected person will, on average, transmit the virus to one to two other people in an influenza outbreak, potentially resulting in rapid propagation of the virus in a population.4, 6, 7
Minor genetic changes that accumulate in seasonal influenza viruses (a process known as “antigenic drift”) make it necessary to reformulate and readminister the influenza vaccine each season.8, 9 With its easy transmissibility and mutability, influenza poses constant challenges that nurses know all too well—from teeming wintertime EDs and pediatric waiting rooms to illness-related absences that strain remaining staff.
Major viral-gene mutations or recombination of two different viral strains of human and animal influenza strains can create a new viral subtype (a process called “antigenic shift”) that's easily transmitted to and among humans.8–10 Isolation and identification of new viral subtypes is necessary for vaccine development, which is itself a complex manufacturing process that currently does not begin to produce doses in quantity for at least six months.11 When a virus for which there is no vaccine becomes easily transmissible among nonimmune people, the opportunity for a pandemic is created.
Figure. In this 1918...Image Tools
The historical record shows many accounts of disease outbreaks that may have been influenza epidemics or pandemics. Although the scale of the outbreaks and their causative agents are not precisely known in many cases, most historians agree that an outbreak that began in Asia in 1580 was an influenza pandemic.12 In the past 300 years, there have been at least 10 influenza pandemics,13, 14 which, by definition, result in moderate to dramatic spikes in illnesses and deaths above average annual levels.15, 16
During the 20th century three pandemics occurred: in 1918–20, 1957–58, and 1968–69 (a fourth worldwide outbreak that began in 1977 is not accepted by all authorities as a true pandemic). The most fearsome of these, the 1918–20 pandemic (see Figure 1, page 53), sickened 25% of the U.S. population in several six-to-eight-week waves and rapidly killed an estimated 2.5% of its victims (the percentage of ill people who die, known as the case fatality ratio, is an important indicator of the severity of the outbreak; in 1918, some populations outside the United States had much higher case fatality ratios).17 Communities were paralyzed for weeks, with hospitals and mortuaries filled beyond capacity, public services severely disrupted, and schools and businesses shuttered. This experience was echoed around the world, and estimates of the global loss of human life range between 30 million and 50 million.18, 19 In contrast, the 1957–58 and 1968–69 pandemics were clinically milder, though they still resulted in worldwide death tolls of 1 million to 2 million, and they are remembered less as disasters than as epidemiologic curiosities in which a single influenza strain was tracked around the world.15 Since the last influenza pandemic a new network of global laboratories and surveillance systems can speed the recognition of an emerging pandemic and the identification of its cause, but influenza pandemics remain difficult to predict.20
WHY WORRY NOW?
Worldwide social and ecologic changes, including a growing human population, crowded living conditions, and rising global mobility, have raised the risk that a virulent influenza strain could spark a particularly devastating pandemic. Larger populations have resulted in higher numbers of food animals, leading to more human–animal interaction and therefore to opportunities for viral-gene recombination and transmission.21 Once a virus adapts to humans, global air travel can greatly accelerate its spread. Since 2003, a pathogenic avian influenza strain, A (H5N1), has caused a pandemic in domestic poultry and wild birds in much of the world, as well as more than 300 laboratory-confirmed human cases, with a 60% case fatality ratio.20 Presently, avian A (H5N1) influenza is not readily transmitted to humans—most of the people who have fallen ill from A (H5N1) had direct exposure to poultry. It is not known whether the A (H5N1) virus will cause a human pandemic.
Prototype vaccines for A (H5N1) are being tested in clinical trials, and small quantities have been stockpiled.22 But a pandemic could be caused by an entirely different influenza subtype, one for which a vaccine won't be available in large enough quantities until at least six months after the strain is isolated.11 Potentially effective antiviral medications are available for treatment, postexposure prophylaxis, or longer-term prophylaxis, and stockpiles are increasing. But the effectiveness of current antivirals against a specific pandemic influenza strain is uncertain, and the medications would need to be administered swiftly—within 48 hours of symptoms appearing—which is a daunting challenge for distribution systems.15 Experience from past influenza pandemics and the ability to monitor for specific pathogens such as the avian A (H5N1) subtype should help inform our nation's readiness for the next pandemic.
In addition to the emergence and spread of the A (H5N1) virus, disasters that have occurred in recent years have made clear the advisability of planning for an influenza pandemic. The outbreak of severe acute respiratory syndrome (SARS) in 2003 startled the global public health community with its virulence, efficient transcontinental transmission, and significant economic effects. Then the devastation caused by Hurricanes Katrina and Rita demonstrated that a large-scale disaster can overwhelm existing emergency response systems. Also, it's only in the past half decade that new information about the 1918 influenza virus and reexamination of the long-lasting effects of that pandemic have returned it to general awareness.10, 15
HOW CAN WE PREPARE?
In both the private and public sectors, and at the federal, regional, state, and local levels, preparations and planning are taking place.
On November 1, 2005, President Bush unveiled the National Strategy for Pandemic Influenza, a document that outlines both government and private sector responsibilities in three areas: preparedness and communications, surveillance and detection, and response and containment.23 A detailed national implementation plan developed from this document charged cabinet-level federal agencies with devising plans to maintain operations, protect employees, communicate with stakeholders, and support federal efforts during a pandemic.11 The plan culminates in a list of action items and performance measures that require federal agencies to work together and with state agencies and private groups, including businesses and faith-based organizations, to prepare for an influenza pandemic (see Table 2, above, for a sample action item that focuses on communications, an area of special concern in large-scale events). A goal of the national strategy and implementation plan is to create and test disaster response and emergency management systems to ensure that a well-prepared, communicative, and operational response will be in place if we are faced with an influenza pandemic of any severity. Already under way are new vaccine development24; federal stockpiling of antiviral medications, personal protective equipment, and health care materiel22; modeling studies to forecast potential outcomes of pandemic interventions25, 26; and a host of detailed plans drafted by federal agencies, states, businesses, schools, and health care systems and facilities.
In February, the Centers for Disease Control and Prevention, in collaboration with numerous public and private agencies, issued planning guidance for “community mitigation measures” during a pandemic. These are specific actions that a community could take to minimize the disease's spread, limit illness and death, and keep essential services operating. The measures would be applied according to the severity of the pandemic and could include treating those who had fallen ill with antiviral medications and providing prophylactic antivirals to their household members, voluntary isolation of the ill and quarantine of household members, school closures and cancellation of public gatherings, and using social distancing measures in the workplace.27
Other planning efforts
The federal government's emphasis on pandemic planning as well as federal funding of states' pandemic planning have spurred planning efforts by regions, states, communities, and the private sector. Nearly all states have plans posted on the Internet. Details vary widely, but state plans include actions they would take in pandemic surveillance, management, and containment, including distribution of antivirals and vaccines.28, 29 Checklists to help businesses, schools, colleges and universities, faith-based organizations, and health care settings with pandemic planning are available at www.pandemicflu.gov. (A quick search of the Internet reveals an abundance of pandemic plans posted from a wide array of sources.) To address concerns about allocating scarce resources during a pandemic, federal agencies have initiated public and private sector collaborations charged with developing prioritization plans for distributing vaccine and antiviral medications.30
WHAT'S THE RIGHT BALANCE?
At every level, from the president's cabinet to rural hospitals, pandemic influenza planning takes time and resources. Preparations are costly and complicated. If you've served in a hospital or community planning group, you may have estimated how many N95 respirators or doses of antiviral medications might be needed in a severe influenza pandemic—and been daunted by the cost and storage requirements. Or perhaps you've faced the administrative conundrum of how to quickly train retired nurses to replace those absent because of illness. And you may have questioned the worth of planning, and the cost of stockpiling resources, when your facility has so many present needs.
But as you grapple with these difficult questions, consider the fact that influenza pandemics will happen because we cannot prevent them. A renowned historian of the 1918–20 pandemic, Alfred W. Crosby, said, “I know how not to get AIDS. I don't know how not to get the flu.”31
Perhaps the 1918 pandemic was a once-in-a-millennium event, or maybe a pandemic caused by a similarly lethal influenza A (H5N1) strain will strike in the next five years. It's wise to plan, always considering how the resources might be useful for other situations. “All hazards” emergency plans are designed to be of use in managing nearly any kind of disaster or emergency. Harking back to the SARS epidemic, every “all hazards” emergency plan should include measures for dealing with any infectious disease outbreak. Your list of retired nurses willing to return to work might prove useful in the aftermath of an earthquake. Immunization clinics for seasonal influenza can help you plan how you will distribute vaccine or antivirals in a pandemic (see Emerging Infections, “Using Seasonal Influenza Clinics for Public Health Preparedness Exercises,” October 2006). The search for an A (H5N1) influenza vaccine has stimulated research that will improve vaccine production in general.24 Finally, think of pandemic planning the way you think of car insurance—as something you must have but hope never to have to use.
Personal Pandemic Planning
Preparing for a disease outbreak is similar to general emergency preparedness.
* Keep essential supplies on hand: nonperishable foods, bottled water, medications, and personal hygiene products.
* Keep your family's health information up-to-date, organized, and accessible.
* Make sure you can communicate from your home by several methods (such as telephone and e-mail) and that you can get information from the outside world (including by battery-powered radio).
* Get an annual seasonal influenza vaccination; it protects you and your contacts from seasonal influenza strains now and from any that might circulate later with a pandemic strain.
* Participate in your facility's emergency planning; get training in the implementation of the plans.
* In case you can't work because of your own or a family member's illness, be prepared to spend an extended period of time at home; have supplies on hand to keep yourself busy.
* Explore the possibility of telecommuting (for example, by assisting with telephone health care advice).
* Contribute to your community's preparedness (for example, by organizing local response planning and being available to help in the event of an outbreak).
Ensuring Effective Risk Communication
6.3.8 Ensure that timely, clear, coordinated messages are delivered to the American public from authoritative sources at all levels of government and assist the governments of affected nations to do the same.
220.127.116.11 HHS, in coordination with DHS, DOD, and VA, shall develop and disseminate a risk communication strategy within 6 months, updating it as required. Measure of performance: implementation of risk communication strategy on www.pandemicflu.gov and elsewhere.
18.104.22.168 DOD and VA, in coordination with HHS, shall develop and disseminate educational materials, coordinated with and complementary to messages developed by HHS but tailored for their respective departments, within 6 months. Measure of performance: up-to-date risk communication material published on DOD and VA pandemic influenza websites, HHS website www.pandemicflu.gov, and in other venues.
HHS = Department of Health and Human Services, DHS = Department of Homeland Security, DOD = Department of Defense, VA = Department of Veterans Affairs.
Face Masks or Respirators?
A press release on May 3 from the Centers for Disease Control and Prevention (CDC) introduced interim guidance for the use of face masks and respirators in public settings during an influenza pandemic, which is summarized at www.pandemicflu.gov/vaccine/maskguidance.html. Here are the three main recommendations in the summary.
* ''Whenever possible, rather than relying on the use of masks or respirators, close contact and crowded conditions should be avoided during an influenza pandemic.
* ''Facemasks should be considered for use by individuals who enter crowded settings, both to protect their nose and mouth from other people's coughs and to reduce the wearers' likelihood of coughing on others; the time spent in crowded settings should be as short as possible.
* “Respirators should be considered for use by individuals for whom close contact with an infectious person is unavoidable. This can include selected individuals who must care for a sick person ([for example, a] family member with a respiratory infection) at home.”
In the press release, Dr. Michael Bell, associate director for infection control in the Division of Healthcare Quality Promotion at the CDC, said, “Facemasks are not designed to protect people from breathing in very small particles, such as viruses…. Rather, facemasks help stop potentially infectious droplets from being spread by the person wearing them…. Respirators are designed to protect people from breathing in very small particles, which might contain viruses. Thus, if you are caring for someone who is ill with pandemic flu, proper use of a well-fitted respirator may be a reasonable choice.”
Dana Carey, associate editor
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New York: Viking; 2004.
2. Dushoff J, et al. Mortality due to influenza in the United States—an annualized regression approach using multiple-cause mortality data. Am J Epidemiol
3. Harper SA, et al. Prevention and control of influenza. Recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Recomm Rep
4. Bridges CB, et al. Transmission of influenza: implications for control in health care settings. Clin Infect Dis
5. Goldmann DA. Transmission of viral respiratory infections in the home. Pediatr Infect Dis J
6. Weiss RA. The Leeuwenhoek Lecture 2001. Animal origins of human infectious disease. Philos Trans R Soc Lond B Biol Sci
7. Longini IM, Jr., et al. Containing pandemic influenza at the source. Science
8. Gabriel G, et al. The viral polymerase mediates adaptation of an avian influenza virus to a mammalian host. Proc Natl Acad Sci USA
9. Kilbourne ED. Influenza pandemics: can we prepare for the unpredictable? Viral Immunol
10. Taubenberger JK, et al. Characterization of the 1918 influenza virus polymerase genes. Nature
12. Potter CW. A history of influenza. J Appl Microbiol
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14. Patterson KD. Pandemic influenza, 1700–1900: a study in historical epidemiology.
Totowa, NJ: Rowman and Littlefield; 1986.
15. Knobler SL, et al., editors. The threat of pandemic influenza: are we ready?
Washington, DC: National Academies Press; 2005.
16. Osterholm MT. Preparing for the next pandemic. N Engl J Med
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2001;116 Suppl 2:32–3.
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19. Patterson KD, Pyle GF. The geography and mortality of the 1918 influenza pandemic. Bull Hist Med
21. Wilson ME. The traveler and emerging infections: sentinel, courier, transmitter. J Appl Microbiol
25. Germann TC, et al. Mitigation strategies for pandemic influenza in the United States. Proc Natl Acad Sci USA
26. Committee on Modeling Community Containment for Pandemic Influenza. Board on Population Health and Public Health Practice. Modeling community containment for pandemic influenza: a letter report.
Washington, DC: Institute of Medicine of the National Academies; 2006. http://www.nap.edu/catalog/11800.html
27. Centers for Disease Control and Prevention. Interim pre-pandemic planning guidance: community strategy for pandemic influenza mitigation in the United States—early targeted, layered use of nonpharmaceutical interventions.
Atlanta: U.S. Department of Health and Human Services; 2007 Feb. http://www.pandemicflu.gov/plan/community/community_mitigation.pdf
28. Holmberg SD, et al. State plans for containment of pandemic influenza. Emerg Infect Dis
31. Kolata GB. Flu: the story of the great influenza pandemic of 1918 and the search for the virus that caused it.
New York: Farrar, Straus and Giroux; 1999.
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