BY MIKE McEVOY
In the fall of 2003, the news media reported on a World Health Organization (WHO) estimate that up to 100 million people worldwide might die if an Asian bird flu outbreak spread to people. Shortly thereafter, photos of an eight-year-old Vietnamese child who died from avian flu spurred fears that the world was on the verge of a bird flu pandemic. Governments scrambled to develop pandemic plans, medical researchers rushed to develop vaccines, and health care systems braced for the impact. Four years have passed without a pandemic. What happened? This article describes influenza, control measures, pandemics, and what you should really expect to happen in the future.
INFLUENZA
Influenza, or the flu, is a respiratory infection transmitted by contact with respiratory secretions from an infected person who is coughing or sneezing. The incubation period, or time from exposure until onset of symptoms, is from one to five days, usually averaging two days. Those infected with influenza are communicable, or can transmit flu to others, for one to two days before onset of symptoms and four to five days afterward. The greatest period of infectivity correlates with fever. Recent studies demonstrate that children remain communicable much longer than adults, ranging from 10 days up to six months. The timing for influenza season depends on where you live. In North America, peak flu season runs between December and March, when cooler weather most favors virus survival. Cooler climates have longer flu seasons, while tropical climates have extremely short or no flu season.
Symptoms of the flu are very similar to other viral illnesses, including rapid onset of fever, chills, body aches, sore throat, nonproductive cough, runny nose, and headache. The distinguishing and most prominent hallmark of the flu compared with other illnesses is sudden onset. Very often, people report feeling that they are “coming down with a cold.” There is no such warning with the flu. One minute, infected people feel perfectly well; the next minute, they are violently ill with fever and disabling symptoms. From that perspective, many of you might realize that illness you previously attributed to influenza was more likely a bad cold or other viral infection.
Respiratory viruses create a three-foot “hot zone” around people. Chance of infection from breathing exhaled respiratory secretions is unlikely beyond this three-foot hot zone, a useful piece of information for EMS providers when approaching any patient with an infection carried in respiratory secretions. Merely keeping your distance from others is not enough to prevent you from getting the flu yourself. Respiratory infections, like most germs, are transmitted from mouths and noses to hands and then onto objects. Doorknobs, telephones, radio microphones, pens, keyboards, dishes, steering wheels, and virtually any other surface in an infected person’s environment can harbor flu virus, waiting for the next person who touches it to pick up the virus on his hands. Influenza viruses survive on nonporous surfaces like plastic and stainless steel for 24 to 48 hours. Cloth, paper, and tissue keep flu viruses alive for eight to 12 hours. If you pick flu virus up from touching an object, it remains viable on your hands for up to five minutes. During that time, all it takes to infect you is touching your mouth or nose.
Influenza is a very serious illness. In the United States alone, 36,000 people die each year from the flu, and more than 200,000 people are hospitalized with influenza complications. Worldwide, the annual death rate has consistently remained at just over 250,000. Those at greatest risk for death and serious complications from the flu are people over 65 years of age (who comprise 85 percent of influenza deaths), those with chronic diseases, infants, pregnant women, and nursing home residents. The influenza attack rate ranges between five and 20 percent of the general population in any given season; nursing home attack rates hover around 60 percent. Vaccination significantly lowers the risk not only of infection but also of transmitting influenza to others. In nursing homes, neonatal nurseries, and other health-care settings, vaccinating workers dramatically reduces deaths from all causes during flu season. Unvaccinated prehospital providers likely serve as carriers of flu virus, infecting not only susceptible patients but also their own families, friends, and coworkers.
There are three types of flu viruses: A, B, and C. Type A causes the most severe illness and has two subtypes. Humans, birds, pigs, horses, and other animals of all ages can be infected with type A flu. Epidemics (local outbreaks) and pandemics (worldwide outbreaks) both result from type A flu viruses. Two subtypes of type A flu virus are the H subtype and the N subtype. There are 15 H subtypes (H1 through H15) and nine N subtypes (N1 through N9). A complete description of a type A flu virus lists both subtypes, as in H5N1 or H3N2. A myth propagated by the media is that humans can be infected with avian flu. Type A flu infections are described by the species infected: avian infections involve birds, equine infections involve horses, and swine infections involve pigs. Unlike some viruses whose natural hosts are human, type A flu virus is hosted in wild birds. Eliminating type A flu virus would require getting rid of all birdshardly practical or possible. For mankind, type A flu virus is here to stay as long as birds fly the skies.
Type B flu viruses result in less severe illness and have no subtypes. They infect humans only, primarily children; cause mild epidemics; and have no ability to produce a pandemic. When elderly patients become infected with type B flu, illness can be quite severe. Annual flu vaccinations protect against two type A and one type B strains of flu virus, based on a consensus best guess of viruses expected to appear each fall.
Type C flu viruses produce very mild to no symptoms. They infect only humans and pigs. Medical literature describes type C influenza as rare, although most children over age 15 have already developed antibodies to type C influenza, suggesting that they were infected at some point.
PANDEMICS
Flu, like all other viruses, changes over the course of time. Small changes in a virus where new strains appear and replace older strains are referred to as antigenic drift. Antibodies in people infected with older strains may or may not work to protect against infection from newer strains. When viruses experience an abrupt, major change resulting in a new subtype or novel strain, antigenic shift is said to have occurred. Antigenic shift has the potential to produce pandemic outbreaks. The criteria for a pandemic, or worldwide outbreak, include a novel virus that all (or most) people are susceptible to, easy transmission from person to person, and conditions allowing for wide geographic spread.
In the 20th century there have been three flu pandemics. The first, in 1918, was caused by an H1N1 virus called the Spanish flu and killed 20 to 40 million people worldwide. In 1957, an H2N2 virus named the Asian flu resulted in one to four million deaths worldwide. The Hong Kong flu of 1968 was caused by an H3N2 virus, also resulting in one to four million deaths worldwide. Although some researchers see patterns in past pandemics suggesting the world is overdue for another, there is no sound basis supporting such a conclusion.
Viruses are normally species specificthat is, they rarely spill over from one family to another. Equine flu tends only to infect horses, avian flu only birds, and swine flu only pigs. Thus the mechanism by which bird flu might spill over into the human species is not understood. The best theory for how such a transfer might occur points to the pig, a species that happens to be susceptible to certain type A flu viruses that infect birds and others that infect people. In theory, a pig infected with a human type A flu virus that simultaneously became infected with an avian type A flu virus could potentially become the viral breeding ground for a new virus. Of course, the pig would have to infect a human with the newly created virus, a process that seems far-fetched but not entirely impossible.
Wild waterfowl have carried type A flu for more than 105 million years. They carry all H and N subtypes in their intestines and rarely develop any symptoms of infection. Waterfowl excrete large amounts of virus into bodies of water they fly over. Domestic birds such as chickens have carried type A influenza for 50 million years. Unlike waterfowl, domestic birds often develop respiratory infections from the virus. They shed influenza in both respiratory secretions and stool. Outbreaks of type A or avian flu among domestic birds are not new. Depending on the severity of the disease, avian flu outbreaks are classified as low pathogenic avian influenza (LPAI) or high pathogenic avian influenza (HPAI). The avian flu form that is now endemic among bird and poultry populations in Asia is an HPAI involving the H5N1 variant of type A flu.
The United States first had cases of HPAI in 1924. A huge outbreak of H5N2 flu in 1983 required the destruction of 17 millions birds on U.S. farms and resulted in a 30 percent increase in egg prices. An Italian outbreak of H7N1 flu in 1999 caused similar havoc and required that 18 million birds be destroyed. Hong Kong suffered avian outbreaks of H5N1 in 1997 and again in 2001. An H5N1 outbreak in Southeast Asia in 2003 took a turn in pattern seen only once before: It spread internationally. What we now know as the avian flu or bird flu is the continued international spread of this highly pathogenic type H5N1 avian influenza.
How the H5N1 avian flu outbreak has traveled from country to country is unclear. One theory is that migratory birds spread the infection along their flight paths, depositing infectious waste into bodies of water as they pass, infecting local birds. Based on migratory bird flight paths, the arrival of the HPAI was expected in Alaska and the U.S. West Coast in fall 2006 and on the U.S. East Coast in spring 2007. That has not yet happened. A second theory is that illegally smuggled infected poultry are passing infection to healthy birds at their destinations. There is much greater evidence supporting this method of transmission, a fact that continues to stymie agricultural and customs officials.
While influenza viruses normally remain species specific, they have at times infected humans. Of bird flu viruses, H5N1, H7N3, H7N7, and H9N2 have occasionally infected people. With the exception of H5N1, human infections from birds have resulted in very mild or extremely limited illness. The overall case fatality rate for humans infected with H5N1 is 56 percent compared with the case fatality rate for human influenza of 0.2 to 0.35 percent. The current outbreak of H5N1 among birds concerns the medical community because of its international spread and alarming case fatality rate.1 Despite these worries, H5N1 remains largely a disease of birds. Since 2003, tens of millions of poultry have been infected, with fewer than 300 human cases. People who got sick from bird flu all had considerable contact with sick birds, touching them with their bare hands and likely contacting infected respiratory secretions and stool. So far, there has been no clearly documented human-to-human transmission.
SHOULD YOU FEAR THE CHICKEN?
It seems only a matter of time before highly pathogenic avian influenza arrives in the United States. Whether it comes with migratory birds or in smuggled poultry, you will probably awaken some morning and read about it on the front page news. Ifor, more appropriately, whenbird flu arrives in the United States, it does not mean people will be infected. Birds, not people, should be afraid. From what we know about type A flu, it is clear that even healthy birds carry germs that can make you ill. You should not handle wild birds. If you touch a wild bird, make sure to wash your hands. Perhaps the H5N1 virus will mutate into a form that readily infects people. That has not happened yet. If it does, the first clue could be health care worker infection from patients. That would demonstrate unmistakable human-to-human transmission and likely signal an ominous change in the virus.
Why have the media and government officials made such a big deal about a potential bird flu pandemic?2 Probably because they correctly recognize that we are incredibly ill prepared. The SARS outbreak in 2002 poignantly illustrated how inadequate our planning and preparation have been. Between November 2002 and August 2003, there were 8,422 reported cases of SARS with 916 deaths. One-quarter of all infections and deaths involved health care workers, clear evidence of an ill-equipped system.
PREPAREDNESS IS KEY
Whether the bird flu ultimately evolves into a full-blown pandemic, the timing could not be more appropriate for you and your department to step up preparedness measures. Two measures every firefighter and EMS provider should immediately take are to intensify routine infection control behaviors and to assess pandemic readiness.
Everyday patient care routines resulted in SARS-infected firefighters and EMS providers. Early in the outbreak, no one understood SARS transmission, and very few EMS services were in the habit of routinely screening patients for infection. Recognizing a potentially infected patient before coming within the three-foot hot zone around that person is imperative for your everyday safety. This is not a practice that should wait until an outbreak is reported.
EMS has been and will again be first to see seriously ill patients from epidemics, pandemics, and virtually any outbreak of disease that comes along. Two features distinguish infectious patients: They appear sick, and they have a high fever or rash. Virtually every infectious illness, known and unknown, throughout the history of medicine has met these criteria. You must determine scene safety by assessing every patient you encounter for these criteria before you enter the three-foot hot zone around that individual.
Rashes are easy to spot; fever is not so easy to assess from a distance. Recent studies of temperature measurement in prehospital and emergency department settings come to remarkably similar conclusions about the equipment available: Nothing is as accurate as patient opinion when it comes to determining the presence of fever. That’s right, no thermometer required. Simply ask your patients if they feel like they have a fever. You can do that from 15 feet away. If they look sick and have a rash or report a fever, the scene is not safe. You must deploy the most important piece of infection control equipment made: an isolation mask for your patient. Toss them a mask and have them put it on before you come any closer. Having patients wear an isolation mask effectively reduces the three-foot hot zone to mere inches. Nothing is more effective at protecting you from infection. This practice needs to be ingrained in our everyday routine. Note that you should give patients simple isolation masks; these filter inhaled and exhaled air. N-95 or N-100 masks filter only inhaled air; such filters would not protect people nearby from exhaled infectious droplets.
Do not ignore hand hygiene, gloves, goggles, isolation gowns, disposables, and other personal protective equipmentthey are all important components of an infection control plan and are all secondary to scene safety. Mask potentially infected patients first, and ask questions later.
The second action you should take immediately is to perform a pandemic readiness assessment. The Centers for Disease Control and Prevention (CDC) provides a very useful EMS Pandemic Planning Checklist.3 Some of the opportunities for improvement often identified with the CDC checklist include closely coordinated preplanning with public health officials and solid awareness of the fire and EMS roles in local, state, and federal pandemic plans. By now, all members of your department should have received training on pandemics and associated infection control measures. You should have a clearly defined and ready to implement pandemic triage and transport plan including 911 center triage protocols when EMS response is unavailable or local hospitals all close.
SARS quickly exhausted the entire supply chain of isolation masks; a pandemic would do the same. Your department should have in storage enough isolation masks and disposable equipment for patients and members to last the duration of a pandemic. Routine vaccination of all members should be a component of your department occupational health plan. Have in place and ready to implement contingency plans for staffing; you can expect a 30 to 40 percent workforce reduction because of member or family illness and childcare issues. Download the entire CDC checklist for an accurate assessment of your pandemic readiness.
Individuals should assess their own readiness as well: Expect food and medical supplies to run short and realize that many services we take for granted probably would not be available. The CDC Pandemic Flu Web site offers a wealth of information to better prepare individuals and families (www.pandemicflu.gov).
The avian flu is not presently a significant threat to people. It is of grave concern to birds. There will most likely be another pandemic in the future; when, where, and what might cause it are extremely difficult to predict.
The SARS outbreak demonstrated that health care providers, including fire and EMS, are very ill prepared. You can start protecting yourself right now by developing a greater awareness of potentially infectious patients, paying better attention to isolation and infection control practices, learning pandemic plans, and assessing both your department and individual pandemic readiness. Don’t wait until tomorrow.
ENDNOTES
1 World Health Organization. Avian Influenza. Retrieved October 7, 2007, from www.who.int.
2 The White House. National Strategy for Pandemic Influenza. Retrieved October 7, 2007 from www.whitehouse.gov/homeland/pandemic-influenza.html.
3 U.S. Department of Health and Human Services. Emergency Medical Services and Non-Emergent (Medical) Transport Organizations Pandemic Influenza Planning Checklist. Retrieved October 4, 2007, from www.pandemicflu.gov/plan/emgncymedical.html.
MIKE McEVOY, Ph.D., REMT-P, RN, CCRN, is the EMS coordinator for Saratoga County, New York, and the EMS director on the board of the New York State Association of Fire Chiefs. Formerly a forensic psychologist, he is a patient care coordinator in cardiac surgery and teaches critical care medicine at Albany Medical College. He is a paramedic for Clifton Park-Halfmoon Ambulance, chief medical officer for the West Crescent (NY) Fire Department, and EMS technical editor for Fire Engineering.
