Avian Influenza
David K. Henderson
Deputy Director for Clinical Care
Clinical Center
National Institutes of Health
About the Lecture
Influenza has been a major public health threat for centuries. Pandemics (world-wide epidemics) of influenza have been well documented for the past four centuries, with the best-studied pandemics being those of 1918 (the Spanish Flu); 1957 (the Asian Flu) and 1968 (the Hong Kong Flu). Substantial attention has been focused over the past year on the increasing potential for a new pandemic, in great measure because of H5N1 “avian” influenza that has spread rapidly around the world in chickens and waterfowl. This presentation will first address influenza in historical context. I will then briefly describe the virology and epidemiology of influenza, as well as the unique biology of influenza viruses, specifically noting how the virus escapes human immunity to produce annual epidemics as well as how the virus changes to produce pandemics. I will briefly address the clinical manifestations associated with influenza virus infection and will relate these findings to the pathology induced by the infection. I will close with a brief discussion of how individuals, communities, and hospitals are approaching the issue of preparedness for a possible pandemic.
About the Speaker
DAVID K. HENDERSON is a graduate of Hanover College, Hanover, Indiana, and the University of Chicago Pritzker School of Medicine. He took his postgraduate training in Internal Medicine and Infectious Diseases at the Harbor-UCLA Medical Center in Torrance California, subsequently joining the faculty at the UCLA School of Medicine in 1978. He then traveled east in 1979 to become the Hospital Epidemiologist at the Clinical Center at the National Institutes of Health in Bethesda, Maryland – a position he still holds. He has subsequently held several positions at NIH, including the roles of Coordinator of AIDS Activities for the Clinical Center from 1985 to 1988; Associate Director of the Clinical Center, from 1988 to 1994; and Acting Clinical Director, from 1991 to 1996. In 1994 he was named Deputy Director for Clinical Care of the Clinical Center. In his current role, he supervises all aspects of clinical care in the Clinical Center and maintains responsibility for hospital epidemiology, clinical quality, emergency preparedness and patient safety at the NIH Clinical Center.
Dr. Henderson has been elected to several professional societies and organizations and has received numerous honors and awards, including the Clinical Center Director’s Award, the NIH Director’s Award (three times), The Secretary of the U.S. Department of Health and Human Service’s Award, and a Special Citation from the General Counsel of the U.S. Department of Health and Human Services. He has been the Academic Councilor to the Society for Healthcare Epidemiology of America. He is a Fellow in the American College of Physicians and a Fellow in the Infectious Diseases Society of America. Beginning in 2001, he was chosen to serve on both the Public Policy Committee as well as the Bioterrorism Workgroup of the Infectious Diseases Society of America. In 2005 he was elected Chair of Division L (Nosocomial Infections) for the American Society for Microbiology and also was appointed at the National Institutes of Health’s liaison to the Healthcare Infection Control Practices Advisory Committee (HICPAC) for DHHS and CDC.
Dr. Henderson has maintained an active research interest in infectious diseases and hospital epidemiology, concentrating in the area of risk for occupational infections in healthcare providers. His work helped define the magnitude of risk for transmission of the human immunodeficiency virus infection in the healthcare setting, publishing on infections among both patients and providers. He has published more than 100 manuscripts in refereed journals in addition to 50 chapters in medical textbooks. He has been an invited speaker at many national and international academic conferences, including those of the International Conference on AIDS, the Annual Conference of the Infectious Diseases Society of America, the Annual Meeting of the American Society for Microbiology, the 3rd and 4th Decennial Conferences on Nosocomial Infections, the Interscience Conference on Antimicrobial Agents and Chemotherapy, the International Conference on Antiretroviral Therapy, and the International Conference of the Hospital Infections Society. He has served as a consultant to the Centers for Disease Control and Prevention on many issues relating to the prevention of transmission of bloodborne and airborne pathogens in the healthcare setting.
Minutes
President William Saalbach called the 2,203rd meeting to order at 8:19 pm March 10, 2006. The minutes of the 2,202nd meeting were read and approved.
Mr. Saalbach then introduced the speaker of the evening, Mr. David K. Henderson of the National Institutes of Health. Mr. Henderson spoke on “Avian Influenza.”
Mr. Henderson said his purpose was to tell us how the country is getting ready for the next pandemic of influenza. History shows there have been pandemics for at least 400 years, and he guesses probably much longer than that. There was a major pandemic in 1510. There was the Spanish flu of 1918, which was first isolated in ferrets. Then there was the Asian flu of 1957, which he remembers personally. He came home from school after football practice looking sick and his mother asked, “What is wrong with you?” Two hours later, he had a temperature of 105F and was hallucinating. His wife thinks to this day that that is what is wrong with him.
Ice science shows conclusively that the 1918 flu was avian. The 1957 and 1968 flus also were a mix of avian and human genes.
Nineteen eighteen looked like Hurricane Katrina. Churches, theaters, and schools were closed. A left-handed batter took his position wearing a mask. A man was not allowed on a streetcar without a mask. Army tent hospitals were full of cots. Sixty or 65% of enlisted men contracted the flu.
The 1918 flu began in Kansas. He hopes the next one will not begin in this country as that would give us a little time to prepare.
U. S. life expectancy took a steep dive in 1918 from 55 to 38 years. The flu killed more people than all the wars of the 20th century.
The good news about bird flu is that, generally, humans don't get it. There have been no isolates of H5N1 in the United States today. There have been only a handful of cases, worldwide, of human to human transmission.
The reservoir of bird flu is waterfowl. While waterfowl are asymptomatic, chickens and other birds die of it. Recently, however, in some parts of the world, ducks and geese are dying of it, too, an ominous development. Then he showed a picture of a dead duck in a sailor suit – Donald Duck. Very ominous.
Swine, cats, and horses get flu. Pigs can get infected with both bird and human flu, which provides a great opportunity for recombination of DNA.
The world is much more mobile than it was. He reported a telling case of people in a plane in Juneau, Alaska. One person was acutely ill with a new strain of influenza. The plane was parked some hours with the air system off. In a clear case of airborne transmission, 91% of the people on the plane were infected and 72% developed symptoms.
In another study of potential airborne transmission, they traced the passengers of a 747 that landed at Los Angeles. Those people on the plane were in 37 states in 24 hours.
The virus changes slightly in every person it infects. It infects mostly respiratory epithelial cells, lots of them, and makes lots of copies of itself. Several generations down, the virus shows little affinity to its ancestors. This is called antigenic drift, and it is why we have to get revaccinated every year.
A pandemic is different. It is a true antigenic shift, such as from HVN2 to H5N1. This is believed to result most commonly when two viruses infect one cell and produce a reassortant virus. The 1918 and 1957 viruses have been documented as antigenic shifts.
If there is no human transmission, why be concerned? The increasing number of bird infections increases the risk of a genetic reassortment. Shift happens.
A pandemic would have a huge cost. There might be 25 to 50 million infections in the United States. Including lost work days, the cost could by $71 to $166 billion. There could be 200,000 deaths. That's not exactly chicken feed.
Why do people feel so sick? Those respiratory epithelial cells that get infected are the ones with cilia, which whip stuff up out of the lungs, into the mouth, where it gets harmlessly swallowed. When infected, the cilia do not whip. The stuff builds up, the lungs lose capacity, and you cough.
He showed a really disgusting picture of a sneeze. A sneeze or a cough can spread 30,000 droplets of infected goo.
The efficacy of the vaccines runs from about 70 to 90%, 30 to 90% in children. Adults have a memory response. When vaccinated, their systems respond to all the strains their bodies have ever seen. For the elderly, the effectiveness is only 23%. Vaccinating health care workers helps protect patients; the infection rate drops from 13.9% to 1.7% when the workers are vaccinated. The elderly are at greatest risk and the most good is done by vaccinating health care workers.
Some new influenza drugs show promise.
Amantadine and rimantadine work as chemoprophylaxes. They work against A viruses but not B viruses. Zanamavir and oseltamivir are neuraminidase inhibitors. They must be given in first two days of infection.
He recommended respiratory etiquette. Avoid touching when practical. Antigerm, antiviral washes are very effective. The vaccines are very effective.
He said airborne control works. It has worked against SARS in every hospital throughout world, even in very poor hospitals. Masks work. He showed a picture of a creative young couple wearing a bra, one cup over each face.
Mr. Henderson thinks we are over the hump this year. Flu is a winter disease, and they don't usually start this late.
Mr. Henderson invited questions.
One person asked if her friend should go on her planned trip to China.
Mr. Henderson said she would not be in much danger. Even the Frank Perdues of the world are safe. The people at risk are the ones in the barns and factories. He recommended the friend not get nose to beak with a chicken.
Asked if he was optimistic, he said that pandemics are rare. The current strain is not a pandemic. Medical care is much better than in 1918. The medical profession and the public are better educated. Preparations are underway.
He was asked about a theory that a disease involving catatonia resulted from the 1918 flu. He was unable to say. Mr. Saalbach volunteered that he had read of a study that indicated that the very low rate of catatonia reported probably resulted from infection by a different virus.
Asked if he thinks globalization will speed up transmission, he said he surely does.
After the talk, Mr. Saalbach presented a plaque to Mr. Henderson commemorating the event. He announced the next meeting and made a pitch for membership. He made the parking announcement. He invited everyone to stay for the social hour.
Finally, at 9:54 pm, he adjourned the 2,203rd meeting to the social hour.
The weather: balmy
The temperature: 18°C
Attendance: 43
Respectfully submitted,
Ronald O. Hietala,
Recording secretary