Course Price  $10.00 Contact Hours  1 Instructions  Study the course, then take the test. You can also print the course and test questions and return later to take the test.

Quicklinks Print this course Take the test How to take a course

Bird Flu (Avian Influenza)

Our courses fulfill continuing nursing education requirements in all 50 states. For more accreditation information, click here.

The information in this course is taken primarily from Centers for Disease Control and Prevention: Avian Influenza (Bird Flu). For more information about avian influenza, go to http://www.cdc.gov/flu/avian. Learning objectives and post test were prepared by Susan Walters Schmid, BA, MA, PhD candidate.

Avian influenza (bird flu) is an infection caused by avian (bird) influenza (flu) viruses. These influenza viruses occur naturally among birds. Wild birds worldwide carry the viruses in their intestines, but usually do not get sick from them. However, avian influenza is very contagious, and some domesticated birds—including chickens, ducks, and turkeys—can become infected and even die.

INFLUENZA TYPES, SUBTYPES, AND STRAINS

There are three types of influenza viruses: A, B, and C. Influenza type A viruses can infect people, birds, pigs, horses, and other animals, but wild birds are the natural hosts for these viruses. Humans can be infected with influenza types A, B, and C. Only influenza A viruses infect birds, and all known subtypes of influenza A viruses can infect birds.

Influenza type A viruses are further divided into subtypes based on two proteins on the surface of the virus. These proteins are hemagglutinin (HA) and neuraminidase (NA). Subtypes of influenza A virus are named according to these proteins. There are sixteen known HA subtypes and nine known NA subtypes of influenza A viruses. Many different combinations of HA and NA proteins are possible, each combination representing a different subtype. For example, an "H7N2 virus" designates an influenza A subtype that has an HA 7 protein and an NA 2 protein. Similarly an "H5N1" virus has an HA 5 protein and an NA 1 protein.

Influenza type B viruses are usually found only in humans. Unlike influenza A viruses, these viruses are not classified according to subtype. Influenza B viruses can cause morbidity and mortality among humans, but in general are associated with less severe epidemics than influenza A viruses. Although influenza type B viruses can cause human epidemics, they have not caused pandemics.

Influenza type C viruses cause mild illness in humans and do not cause epidemics or pandemics. These viruses are not classified according to subtype.

Strains

Influenza B viruses and subtypes of influenza A virus are further characterized into strains. There are many different strains of influenza B viruses and of influenza A subtypes. New strains of influenza viruses appear and replace older strains. This process occurs through antigenic drift (described later in this course). When a new strain of human influenza virus emerges, antibody protection that may have developed after infection or vaccination with an older strain may not provide protection against the new strain. Therefore, the influenza vaccine is updated on a yearly basis to keep up with the changes in influenza viruses.

AVIAN INFLUENZA

Avian influenza viruses (type A) circulate among birds worldwide. Certain birds, particularly water birds, act as hosts for influenza viruses by carrying the virus in their intestines and shedding it. Infected birds shed influenza virus in their saliva, nasal secretions, and feces. Susceptible birds become infected when they have contact with contaminated secretions or excretions or with surfaces that are contaminated with secretions or excretions from infected birds. Fecal-to-oral transmission is the most common mode of spread between birds.

Domesticated Birds

Domesticated birds may become infected with the avian influenza virus through direct contact with infected waterfowl or other infected poultry, or through contact with surfaces (such as dirt or cages) or materials (such as water or feed) that have been contaminated with the virus. People, vehicles, and other inanimate objects such as cages can be vectors for the spread of the influenza virus from one farm to another. When this happens, outbreaks of bird flu can occur among poultry.

Infection with avian influenza viruses in domestic poultry causes two main forms of disease that are distinguished by low and high extremes of virulence—low pathogenic avian influenza (LPAI) or highly pathogenic avian influenza (HPAI). LPAI may go undetected and usually causes only mild symptoms (such as ruffled feathers and a drop in egg production). However, HPAI spreads more rapidly through flocks of poultry. This form may cause disease that affects multiple internal organs and has a mortality rate that can reach 90% to 100%, often within 48 hours.

Other Wild and Domesticated Animals

Research suggests that currently circulating strains of H5N1 viruses are becoming more capable of causing disease (pathogenic) in animals than were earlier H5N1 viruses. One study found that ducks infected with H5N1 virus are now shedding more virus for longer periods without showing symptoms of illness. This finding has implications for the role of ducks in transmitting disease to other birds and possibly to humans as well.

Additionally, other findings have documented H5N1 virus infection among pigs in China and Vietnam; H5N1 virus infection of cats (experimental infection of housecats in the Netherlands, isolation of H5N1 virus from domestic cats in Germany and Thailand, and detection of H5N1 viral RNA in domestic cats in Iraq and Austria); H5N1 virus infection of dogs (isolation of H5N1 virus from a domestic dog in Thailand); and isolation of H5N1 viruses from tigers and leopards at zoos in Thailand).

In addition, H5N1 virus infection in a wild stone marten (a weasel-like mammal) was reported in Germany and in a wild civet cat in Vietnam. Avian influenza A (H5N1) virus strains that emerged in Asia in 2003 continue to evolve and may adapt so that other mammals may be susceptible to infection as well.

The American Veterinary Medical Association (AVMA) maintains a website with current information about avian flu and animals. The CDC, USDA, and the AVMA, along with other veterinary associations, are working cooperatively on this issue and healthcare professionals can keep abreast of information through these agencies.

TRANSMISSION TO HUMANS

Although avian influenza A viruses usually do not infect humans, rare cases of human infection with avian influenza A viruses have been reported. Most human infections with avian influenza A viruses have occurred following direct contact with infected poultry. Human clinical illness from infection with avian influenza A viruses has ranged from eye infections (conjunctivitis) to severe respiratory disease (pneumonia) to death.

Since November 2003, nearly 400 cases of human infection with highly pathogenic avian influenza A (H5N1) viruses have been reported by more than a dozen countries in Asia, Africa, the Pacific, Europe and the Near East. Highly pathogenic avian influenza A (H5N1) viruses have never been detected among wild birds, domestic poultry, or people in the United States. Most human cases of H5N1 virus infection are thought to have occurred as a result of direct contact with sick or dead infected poultry.

Other subtypes of avian influenza A viruses also have infected humans, including low pathogenic and highly pathogenic virus strains. Public health authorities closely monitor outbreaks of human illness associated with avian flu because of concerns about the potential for more widespread infection in the human population.

The spread of avian influenza A viruses from one ill person to another has been reported very rarely, and has been limited, inefficient, and unsustained. However, because avian influenza A viruses have the potential to change and gain the ability to spread easily between people, monitoring for human infection and person-to-person transmission is important.

Two main risks to human health from avian flu are:

• The risk of direct infection when the virus passes from the infected bird to humans, sometimes resulting in severe disease
• The risk that the virus—if given enough opportunities—will change into a form that is highly infectious for humans and spreads easily from person to person.

The World Situation

Outbreaks of avian influenza H5N1 occurred among poultry in eight countries in Asia—Cambodia, China, Indonesia, Japan, Laos, South Korea, Thailand, and Vietnam—during late 2003 and early 2004. At that time, more than 100 million birds in the affected countries either died from the disease or were killed in order to try to control the outbreaks. By March 2004 the outbreak was reported to be under control.

Beginning in June 2004, however, new outbreaks of influenza H5N1 among poultry and wild birds were reported in Asia. Since that time, the virus has spread. Reports of H5N1 infection in wild birds in Europe began in mid-2005. In early 2006, influenza A H5N1 infection in wild birds and poultry were reported in Africa and the Near East.

Human cases of influenza A (H5N1) infection have been reported on all populated continents except North and South America. For the most current information about avian influenza and cumulative case numbers, see the World Health Organization Avian Influenza website (listed in Resources).

Of the few avian flu viruses that have crossed the species barrier to infect humans, H5N1 has caused the largest number of detected cases of severe disease and death in humans. In the current outbreaks in Asia and Europe, more than half of those infected with the virus have died. Most cases have occurred in previously healthy children and young adults. However, it is possible that the only cases currently being reported are those in the most severely ill people, and that the full range of illness caused by the H5N1 virus has not yet been defined.

In June 2008 the CDC released results of a new study that suggest that some strains of North American avian influenza A H7 virus "have properties that might enhance their potential to infect humans as well as their potential to spread from human to human." Additional information and a link to the study may be found on the CDC avian flu website.

Drift and Shift

Influenza viruses can change in two different ways. One is antigenic drift, which occurs through small changes in the virus that happen continually over time. Antigenic drift produces new virus strains that may not be recognized by antibodies to earlier influenza strains. This process works as follows: A person infected with a particular flu virus strain develops antibodies against that virus. As newer virus strains appear, the antibodies against the older strains no longer recognize the "newer" virus, and infection with a new strain can occur. This is one of the reasons people can get the flu more than once.

The other type of change is antigenic shift. Antigenic shift refers to an abrupt, major change to produce a novel influenza A virus subtype in humans that was not currently circulating among people.

Antigenic shift can occur either through direct animal (poultry)-to-human transmission or through mixing of human influenza A and animal influenza A virus genes to create a new human influenza A subtype virus through a process called genetic reassortment. Antigenic shift results in a new influenza A subtype. If a new subtype of influenza A virus is introduced into the human population, and most people have little or no protection against the new virus, and if the virus can spread easily from person to person, a pandemic (worldwide spread) may occur.

Influenza viruses are changing by antigenic drift all the time, but antigenic shift happens only occasionally. Influenza type A viruses undergo both kinds of changes.

Reassortment and Transmission

There are substantial genetic differences between the subtypes of influenza A viruses that typically infect both people and birds. Within these subtypes there are also different strains. Influenza A viruses normally seen in one species sometimes can cross over and cause illness in another species.

Although it is unusual for people to get influenza virus infections directly from animals, sporadic human infections and outbreaks caused by certain avian influenza A viruses and pig influenza viruses have been reported. These sporadic human infections and outbreaks, however, rarely result in sustained transmission among humans.

Avian influenza A viruses may be transmitted from animals to humans in two main ways:

• Directly from birds or from avian virus–contaminated environments to people.
• Through an intermediate host, such as a pig.

Influenza A viruses have eight separate gene segments. The segmented genome allows influenza A viruses from different species to mix and create a new influenza A virus if viruses from two different species infect the same person or animal. For example, if a pig were infected with a human influenza A virus and an avian influenza A virus at the same time, the new replicating viruses could mix existing genetic information and produce a new virus that had most of the genes from the human virus (reassortment), but a hemagglutinin and/or neuraminidase from the avian virus.

The resulting new virus might then be able to infect humans and spread from person to person, but it would have surface proteins (hemagglutinin and/or neuraminidase) not previously seen in influenza A viruses that infect humans. This type of major change in the influenza A viruses would be an example of antigenic shift. If this new virus caused illness in people and could be transmitted easily from person to person, an influenza pandemic could occur.

It is possible that the process of genetic reassortment could occur in a human who is co-infected with avian influenza A virus and a human strain of influenza A virus. The genetic information in these viruses could reassort to create a new virus with a hemagglutinin from the avian virus and other genes from the human virus.

Theoretically, influenza A viruses with a hemagglutinin against which humans have little or no immunity that have reassorted with a human influenza virus are more likely to result in sustained human-to-human transmission and pandemic influenza. Therefore, careful evaluation of influenza viruses recovered from humans who are infected with avian influenza is very important to identify re-assortment if it occurs.

SYMPTOMS, DIAGNOSIS, PREVENTION, AND TREATMENT IN HUMANS

The reported signs and symptoms of avian influenza in humans have ranged from eye infections (conjunctivitis) to influenza-like illness symptoms (eg, fever, cough, sore throat, muscle aches) to severe respiratory illness (eg, pneumonia, acute respiratory distress, viral pneumonia) sometimes accompanied by nausea, diarrhea, vomiting and neurologic changes.

A laboratory test is needed to confirm avian influenza in humans. Studies done in laboratories suggest that the prescription medicines approved in the United States for human influenza viruses should work in treating avian influenza infection in humans. However, influenza viruses can become resistant to these medications, so they may not always work.

The CDC and the World Health Organization (WHO) recommend oseltamivir, a prescription antiviral medication, for treatment and prevention of human infection with avian influenza A viruses. Analyses of available H5N1 viruses circulating worldwide suggest that most viruses are susceptible to oseltamivir. However, some evidence of resistance to oseltamivir has been reported in H5N1 viruses isolated from some human H5N1 cases. Monitoring for antiviral resistance among avian influenza A viruses is important and ongoing.

There is currently no commercially available vaccine to protect humans against the H5N1 virus being seen in Asia and Europe. However, in April 2007 the U.S. Food and Drug Administration announced approval of a vaccine that has been added to the National Stockpile. The announcement included the following information:

The vaccine was obtained from a human strain and is intended for immunizing people 18 through 64 years of age who could be at increased risk of exposure to the H5N1 influenza virus contained in the vaccine. H5N1 influenza vaccine immunization consists of two intramuscular injections, given approximately one month apart. The manufacturer, Sanofi Pasteur Inc., will not sell the vaccine commercially. Instead, the vaccine has been purchased by the federal government for inclusion within the National Stockpile for distribution by public health officials if needed (FDA, 2007).

Research continues on numerous other vaccines and on the side effects and efficacy of vaccines. Information for ongoing projects may be found at the U.S. National Institutes of Health clinical trials website and on the CDC avian flu website.

Currently, wearing a mask is not recommended for routine use (eg, in public) for preventing influenza exposure. In the United States, disposable surgical and procedure masks have been widely used in healthcare settings to prevent exposure to respiratory infections, but the masks have not been used commonly in community settings such as schools, businesses, and public gatherings.

There is no evidence that properly cooked poultry or eggs can be a source of infection for avian influenza viruses. The U.S. government carefully controls domestic and imported food products, and in 2004 issued a ban on importation of poultry from countries affected by avian influenza viruses, including the H5N1 strain. This ban is still in place.

INFECTION CONTROL FOR HEALTHCARE WORKERS

The Centers for Disease Control and Prevention (CDC) has issued interim recommendations, based on what are deemed optimal precautions, for protecting individuals involved in the care of patients with highly pathogenic avian influenza and for reducing the risk of viral re-assortment (ie, mixing of genes from human and avian viruses).

The ability of low-pathogenic avian influenza viruses to cause infection and serious disease is less well established, but appears to be lower than that of highly pathogenic viruses based on available information. Nonetheless, it is considered prudent to take precautions to the extent feasible when caring for patients with known or possible avian flu.

Rationale for Enhanced Precautions

Human influenza is thought to transmit primarily via large respiratory droplets. Standard Precautions plus Droplet Precautions are recommended for the care of patients infected with human flu. However, given the uncertainty about the exact modes by which bird flu may first transmit between humans, additional precautions may be prudent for healthcare workers involved in the care of patients with documented or suspected avian flu. The rationale for the use of additional precautions for avian flu as compared with human flu include the following:

• The risk of serious disease and increased mortality from highly pathogenic avian flu may be significantly higher than from infection by human flu viruses.
• Each human infection represents an important opportunity for avian flu to further adapt to humans and gain the ability to transmit more easily among people.
• Although rare, human-to-human transmission of avian flu may be associated with the possible emergence of a pandemic strain.

Recommendations for Avian Flu

All patients who present to a healthcare setting with fever and respiratory symptoms should be managed according to recommendations for respiratory hygiene and cough etiquette (http://www.cdc.gov/flu/professionals/infectioncontrol/resphygiene.htm) and questioned about their recent travel history.

Patients with a history of travel within ten days to a country with avian flu activity who are hospitalized with a severe febrile respiratory illness, or are otherwise under evaluation for avian flu, should be managed using isolation precautions identical to those recommended for patients with known Severe Acute Respiratory Syndrome (SARS). These include:

• Standard Precautions
• Pay careful attention to hand hygiene before and after all patient contact or contact with items potentially contaminated with respiratory secretions.
• Contact Precautions
• Use gloves and gown for all patient contact.
• Use dedicated equipment such as stethoscopes, disposable blood pressure cuffs, disposable thermometers, etc.
• Eye protection (ie, goggles or face shields)
• Wear when within three feet of the patient.
• Airborne Precautions
• Place the patient in an airborne isolation room (AIR). Such rooms should have monitored negative air pressure in relation to corridor, with 6 to 12 air changes per hour (ACH), and exhaust air directly outside or have recirculated air filtered by a high-efficiency particulate air (HEPA) filter. If an AIR is unavailable, contact the healthcare facility engineer to assist or use portable HEPA filters to augment the number of ACH.
• Use a fit-tested respirator, at least as protective as a National Institute of Occupational Safety and Health (NIOSH)–approved N-95 filtering face piece (ie, disposable) respirator, when entering the room.

Additional information regarding these and other healthcare isolation precautions is available on the CDC website. These precautions should be continued for fourteen days after onset of symptoms or until either an alternative diagnosis is established or diagnostic test results indicate that the patient is not infected with influenza A virus. Patients managed as outpatients or hospitalized patients discharged before fourteen days with suspected avian flu should be isolated in the home setting on the basis of principles outlined for the home isolation of SARS patients.

Vaccination of Healthcare Workers

Healthcare workers involved in the care of patients with documented or suspected avian flu should be vaccinated with the most recent seasonal human flu vaccine. In addition to providing protection against the predominant circulating influenza strain, this measure is intended to reduce the likelihood of a healthcare worker's being co-infected with human and avian strains, where genetic rearrangement could take place, leading to the emergence of potential pandemic strain.

Monitoring of Healthcare Workers

Healthcare workers need to be vigilant for the development of fever, respiratory symptoms, and/or conjunctivitis (ie, eye infections) for one week after last exposure to avian influenza–infected patients. Healthcare workers who become ill should seek medical care and, prior to arrival, notify their healthcare provider that they may have been exposed to avian flu. In addition, employees should notify occupational health and infection control personnel at their facility.

With the exception of visiting a healthcare provider, healthcare workers who become ill should be advised to stay home until twenty-four hours after resolution of fever, unless an alternative diagnosis is established or diagnostic tests are negative for influenza A virus. While at home, ill persons should practice good respiratory hygiene and cough etiquette (http://www.cdc.gov/flu/professionals/infectioncontrol/resphygiene.htm) to lower the risk of transmission of virus to others.

STAYING INFORMED, BEING PREPARED

The U.S. Department of Health and Human Services maintains a comprehensive website at http://www.pandemicflu.gov. The following material is derived from that site. Healthcare professionals will find there a wealth of additional information and links to resources at all levels.

What Is a Pandemic?

A pandemic is a global disease outbreak. A flu pandemic occurs when a new influenza virus emerges for which people have little or no immunity, and for which there is no vaccine. The disease spreads easily person-to-person, causes serious illness, and can sweep across a country and around the world in very short time.

It is difficult to predict when the next flu pandemic will occur or how severe it will be. Wherever and whenever a pandemic starts, everyone around the world is at risk. Countries might, through measures such as border closures and travel restrictions, delay arrival of the virus, but they cannot stop it.

Health professionals are concerned that the continued spread of a highly pathogenic avian H5N1 virus across eastern Asia and other countries represents a significant threat to human health. The H5N1 virus has raised concerns about a potential human pandemic because:

• It is especially virulent.
• It is being spread by migratory birds.
• It can be transmitted from birds to mammals and in some limited circumstances to humans.
• Like other influenza viruses, it continues to evolve.

Potential Impact of a Pandemic

A pandemic may come and go in waves, each of which can last for 6 to 8 weeks. An especially severe flu pandemic could lead to high levels of illness, death, social disruption, and economic loss. Everyday life would be disrupted because so many people in so many places become seriously ill at the same time. Impacts can range from school and business closings to the interruption of basic services such as public transportation and food delivery.

A substantial percentage of the world's population will require some form of medical care. Healthcare facilities can be overwhelmed, creating a shortage of hospital staff, beds, ventilators and other supplies. Surge capacity at nontraditional sites such as schools may need to be created to cope with demand.

The need for vaccine is likely to outstrip supply and the supply of antiviral drugs is also likely to be inadequate early in a pandemic. Difficult decisions will need to be made regarding who gets antiviral drugs and vaccines.

Death rates are determined by four factors:

• Number of people who become infected
• Virulence of the virus
• Underlying characteristics and vulnerability of affected populations
• Availability and effectiveness of preventive measures

Preparation

The United States has been working closely with other countries and the World Health Organization (WHO) to strengthen systems to detect outbreaks of influenza that might cause a pandemic. The effects of a pandemic can be lessened if preparations are made in advance. The Department of Health and Human Services and other federal agencies are providing funding, advice, and other support to states to assist with pandemic planning and preparation. Information on international as well as state/federal planning and cooperation, including links to state pandemic plans, is available at http://www.pandemicflu.gov.

Education and outreach are critical to preparing for a pandemic. Understanding what a pandemic is, what needs to be done at all levels to prepare for pandemic influenza, and what could happen during a pandemic helps people to make informed decisions. Well-informed healthcare professionals may be able to help others in their communities in this endeavor.

Pandemic influenza planning checklists are available at the pandemic flu website. These checklists address three areas: creating a structure for planning and decision making, developing a written pandemic flu plan, and elements of a pandemic flu plan. Individual checklists in downloadable format are available for the following: state and local government, business, individuals and families, schools, healthcare providers (of all types), and faith-based and community organizations.

Currently a number of guidance documents relevant to avian flu are being drafted and may be open for public comment. Notice of drafts and public comment periods may be viewed at http://www.pandemicflu.gov.

Posted July 17, 2008

Expires July 1, 2010

Copyright © 2008 Wild Iris Medical Education. All rights reserved.

Accreditation   Home
Site Map   Contact   Privacy   Disclaimer

NursingCEU.com is a division of Wild Iris Medical Education
© 2008 Wild Iris Medical Education, Inc.