23 November 2005
Human Contraction of Bird Flu Rare, Public Health Expert Says
Avian influenza, pandemic threat discussed in State Department webchat
Dr. Karen Smith, public health director for Napa County, California, discussed the public health consequences of bird flu (avian influenza) during an Internet chat November 23.
“It is very important to keep in mind that avian influenza is currently a problem almost exclusively in BIRD populations and in limited areas of the world,” Smith said in the webchat, hosted by the U.S. Department of State. “Remember that despite millions of exposures, only 126 human cases have been documented to date and there is currently no evidence of person-to-person transmission of this virus.”
As of November 25, the World Health Organization had reported 132 human cases of bird flu.
“To date the only humans to develop avian influenza are those with direct contact with poultry,” she said.
Smith discussed the worldwide surveillance for new outbreaks of the virus -- Highly Pathogenic Avian Influenza (HPAI) H5N1 -- in domestic flocks and migratory birds, as well as surveillance for human cases.
She also answered a range of questions on the characteristics of the bird flu virus, transmission of the virus, prevention measures, international preparations for a pandemic and related issues.
For additional information on the avian influenza and efforts to combat it, see Bird Flu.
Following is a transcript of the webchat:
U.S. Department of State
Bureau of International Information Programs (IIP)
Internet Chat: Bird Flu and Public Health
November 23, 2005
Moderator: Welcome to today’s webchat on bird flu with Dr. Karen Smith, public health director of Napa County, California. Smith, a physician specializing in infectious disease and public health, has worked in local public health in California for 10 years. She completed her medical training and infectious diseases fellowship at Stanford University, Stanford, California, after obtaining a master of public health degree in international health at Johns Hopkins University in Baltimore. Prior to her medical training she worked in communicable disease control in Morocco and Thailand.
Dr. Smith will try to respond to as many questions as possible. Unfortunately, due to time limitations, it won’t be possible to answer every question. The official U.S. government Website for pandemic flu information can be found at: http://www.pandemicflu.gov/
Dr. Karen Smith:
I’d like to make some introductory comments: Several factors have led to increased concern during the current avian influenza outbreak caused by a virus called “Highly Pathogenic Avian Influenza H5N1.”(HPAI H5N1).
The virus is now spreading to birds in neighboring countries probably along the migratory pathways. There is evidence that some infected birds may survive and excrete virus for at least 10 days increasing their ability to spread the virus to distant flocks.
This virus also appears to be highly pathogenic to humans. Between December of 2003 and November 14, 2005, there have been 126 confirmed human cases of avian influenza and 64 deaths. H5N1 viruses in general mutate rapidly and show a propensity to acquire genes from influenza viruses infecting other species. This ability means the virus has the potential for antigenic shift and has a resulting pandemic potential.
A pandemic is an epidemic occurring over a wide geographic area and affecting a large proportion of the population. Influenza pandemic occurs when a novel virus, to which no one has immunity, emerges in the human population. Unlike a “usual” influenza epidemic, a pandemic would likely show morbidity in all age groups rather than just the very young and old and would not be seasonal. It is unlikely that there would be adequate stocks of an effective vaccine available before at least 12 -18 months into the pandemic at the earliest. Previous pandemics include the 1918-19 “Spanish/Swine flu” (H1N1), the 1957-58 “Asian flu” (H2N2) and the 1968-69 “Hong Kong flu” (H3N2).
The mortality resulting from these pandemics ranged from an estimated 550,000 deaths in the US in 1918 to 34,000 US deaths in 1968. It just isn’t possible to predict the magnitude of any pandemic before it occurs. Despite the very real possibility of influenza pandemic in our future, there are several things to keep in mind about the current worldwide situation.
Despite the fact that this H5N1 virus has been circulating since late 2003 -- resulting in literally millions of individual human exposures to infected birds -- only 126 human cases have been documented to date and there is currently no evidence of person-to-person transmission of this virus. For this, or any, influenza virus to develop pandemic potential several criteria must be met. The virus must easily infect humans, it must be transmissible from person to person, and it must retain its virulence in order to result in significant morbidity or mortality. These criteria have not been met and there is no way to predict when, if ever, they will be.
Q -- Chrys: As I am in Australia, this topic is currently generating some interest. Can you please advise me on any precaution methods that I need to implement?
A -- Dr. Karen Smith: It is very important to keep in mind that avian influenza is currently a problem almost exclusively in BIRD populations and in limited areas of the world. Remember that, despite millions of exposures, only 126 human cases have been documented to date and there is currently no evidence of person-to-person transmission of this virus.
Personal precautions are only necessary for people with exposure to potentially infected birds. To date the only humans to develop avian influenza are those with direct contact with poultry. In particular, plucking and preparing diseased birds, handling fighting cocks, playing with poultry, and consumption of duck’s blood or possibly undercooked poultry have been implicated in transmission to humans. There have been cases where tigers and leopards in zoos have been infected after feeding with uncooked infected birds.
There is intense worldwide surveillance for new outbreaks of the H5N1 Highly Pathogenic Avian Influenza (HPAI) in domestic flocks and migratory birds. If an outbreak is detected, several control measures are immediately put into place including culling of the infected flocks, environmental disinfection where possible, restriction of movement of birds into and out of the affected area, and increased surveillance in surrounding areas. Efforts are made to obtain testing for H5N1 on hospitalized persons with clinically compatible syndromes in areas known to have circulating virus.
In the U.S., we are increasing surveillance for human cases by requesting that physicians send respiratory specimens for influenza strain typing from patients hospitalized with a clinical syndrome consistent with influenza who ALSO have a recent travel history to an area of the world with known outbreaks of avian influenza in birds or confirmed human cases of avian influenza.
Q -- Brandi: Is the avian influenza similar to the Spanish flu from 1918? Is there any way the genetic reconstruction of this dangerous 1918 influenza has anything to with today's 'bird flu' (avian flu)?
A -- Dr. Karen Smith: The two viruses are similar only in that both are considered to have developed first as avian viruses (for the 1918 strain this is based on the genotype analysis) and both are type A influenza. The 1918 virus was, however, an H1N1 virus while current strain of concern is an H5N1.
Q – William: a. What is the dormant period of the virus?
b. What is the number of contaminated fowls transmitting the virus? Does this include local varieties of birds.?…. pigeons?
A -- Dr. Karen Smith: I assume you mean the incubation period [time from infection to disease]. The WHO review article states, “The incubation period of avian influenza A (H5N1) may be longer than for other known human influenzas. In 1997, most cases occurred within 2-4 days after exposure; recent reports indicate similar intervals but with ranges of up to 8 days.
”A wide variety of species of birds are capable of being infected with the H5N1 virus. The primary wild birds species affected by HPAI H5N1 are ducks, geese, and swans, but also gulls. Among domestic flocks the same species but also chickens are highly susceptible. I’m not aware of the frequency of infection of other types of birds.
Q – William: Can affected corpses contaminate water supplies? How will the burial of bird flu victims be handled?
Will troops remain in areas of infection?
A -- Dr. Karen Smith: Because avian influenza viruses are shed in large quantities in the feces of infected birds and may persist for some days in the right environment. For this reason, environmental decontamination of areas where large numbers of dead birds have been found may be attempted. This is not usually possible, however in the wild. Again, it is important to remember that there is NO widespread human disease at this time. Even in the event of a large-scale influenza pandemic human corpses do not pose a risk for transmission of influenza viruses in water or otherwise (some autopsy procedures could confer some risk if infected lung material were aerosolized). [November 23, 2005 09:59]
Q – William: Is there a specific length of time that is safe for the preparation of eggs? Some individuals eat "soft boiled eggs" while others who may eat them raw, or by other preparation methods.
A -- Dr. Karen Smith: While it would be preferable to avoid eating eggs from flocks with known avian influenza, eggs that are carefully washed should not pose a health hazard. It is the shell that is potentially contaminated if it were in contact with feces from infected birds. Even cooking for a short period of time should inactivate any influenza virus on the exterior of the shell.
Q – William: Are there contingency plans for cancellation of flights, ships? Will space shuttle flights be affected? How long can a quarantine be imposed on a country?
A -- Dr. Karen Smith: Every country would respond to a pandemic in different ways. In the early stages of a pandemic, when affected areas are localized, some level of surveillance and/or control of persons entering a country from an affected area would likely be one of the measures put in place. Such measures could range from symptom screening prior to departure and/or upon arrival (as we saw during SARS) to canceling flights from affected areas. While some of these measures may have some impact on the spread of the disease, such impact is likely to be temporary. Once the disease in question is established in an area, there would be no further use in canceling flights to or from other areas.
I really can’t speak to the space shuttle flights except to say that, in a really large pandemic with many, many sick people, it is likely that most large organizations, including governments would necessarily have to limit their activities to those that are required to “stay in business” as a large portion of the workforce would likely be at home either sick or caring for sick family members.
It isn’t really possible to impose quarantine on a country. Quarantine generally refers to restrictions placed on the movements of people within an area that is affected by a disease.
Quarantine can only be imposed by those with legal control over the area in question. Thus the government of Country A can impose quarantine on certain of its citizens or even places within that country, but no other country could impose a quarantine on Country A. Country B could, however, refuse to import birds or allow people from Country A to enter Country B, but that would not be a quarantine.
When quarantine is imposed on a person or area, the duration of that quarantine depends on the legal authority imposing the quarantine. In California, for example, quarantine would be imposed on someone who appears well (i.e. is not sick), but has been exposed to a communicable disease and is within the incubation period of the disease. That person presents a risk to others with whom s/he comes into contact because s/he could develop the disease and spread it to those others. In this case, the person under quarantine can only be restricted until the incubation period of the disease has passed. At that point, if that person has not become sick, we know that s/he will not become sick and, therefore, no longer poses a risk to anyone else and quarantine must end. Ours law is written so that the duration of quarantine depends on the disease in question. If it is not yet established, the duration of quarantine is determined by the local Public Health Officer but must be supported by science.
Q -- Micheline: Are you monitoring wild birds for evidence of avian flu?
What would be the scenario if migratory birds were found to be positive for the strains of H5 that are of particular concern for mutating to a virus transmissible from human to human?
A -- Dr. Karen Smith: Both state and federal agencies are monitoring for die offs among migratory waterfowl. When a die off is seen, the birds are tested for influenza viruses. If HPAI H5N1 were detected, all local public health, agricultural commissioners and other local and state agencies would be notified. Increased surveillance among domestic flocks would then occur. Poultry farmers would be given instructions on how to protect their flocks from coming into contact with wild waterfowl, as this is believed to be the main route of introduction of the virus into domestic flocks. In addition restrictions on the movement of domestic birds into and out of the affected area would likely be put in place. Culling of wild flocks has not been shown to be effective and would probably not be done. If domestic flocks were affected, however, those flocks would be culled and the environment disinfected.
Q -- Mikhail M.: The other day the Chief Sanitary Officer of Russia, Gennady Onishchenko, warned that the next outbreak of "bird flu" is likely to occur in spring when birds start migrating from south to north. Do you share this concern?
A -- Dr. Karen Smith: While the evidence for the role migratory birds is not yet entirely conclusive, it does seem to be increasingly clear that they may be the primary means by which the virus moves into new geographic regions. That said, we would expect to see the virus continue to spread along the routes that are currently affected. I'm not an expert on what those routes are and would defer to your experts. In the US, we are operating on the assumption that the virus will eventually move into territory here as well, but no one is yet predicting when that might occur.
Q -- Viktor U., Novosibirsk: Russia, in spite of being close to the Asian sources of bird flu, has not registered a single case of it. Could it be that the Slavs are somehow unique in not being vulnerable to the infection?
A -- Dr. Karen Smith: In fact, there are numerous areas where avian cases have been detected but no human cases have arisen. The WHO Website has some good maps that show this. All human cases to date have been associated with outbreaks in domestic flocks as exposure to infected domestic birds has been the route of acquisition of human infection. You would not expect to see human cases if outbreaks in domestic flocks have not occurred.
Q -- Nina P. Krasnodar: Can the spread of bird flu affect the supplies of American chicken meat to Russia?
A -- Dr. Karen Smith: Unless there were large-scale outbreaks of avian influenza in domestic chicken flocks in the U.S., there would be no reason for Russia to restrict movement of U.S. chicken into the country.
Q – Ellena: What is a time frame for diagnostic test? Diagnostic test could be done safely only at the high level of biosecurity labs and there are not many of them even in the big cities.
How well are those labs in North American cities prepared to handle large volumes of samples during pandemics?
Is it a requirement for the test to be confirmed at the WHO labs?
A -- Dr. Karen Smith: The turn-around time for the test will depend on several factors including the transport time of the specimen and the frequency with which the lab runs the test. The test itself does not take long, but most laboratories would need to batch specimens. There is a major push in the U.S. right now to ensure that all the labs in the U.S. "Laboratory Response Network" -- a network of Public Health Labs have the capacity to do at least the initial typing tests for influenza A and that the higher level labs are doing actual strain typing. Few, if any, private labs are set up to do strain typing of influenza viruses.
As to confirmation at WHO, since we are in a surveillance phase, where it is crucial that we know where the virus is and how it is moving, it is critical that reported cases are confirmed as H5N1. Remember that influenza A is common. So cases are currently counted only if confirmed by a WHO-associated lab. Were there a large epidemic where H5N1 was the predominant strain circulating, it would probably not be necessary to confirm.
Q – Ellena: For how long does the virus survive in the environment?
Is virus susceptible to UV germicidal lamps? If yes, what is the time frame for disinfection in patient room, anteroom?
How should waste from patient rooms be handled safely, after being placed in plastic bags? Is the surface of a plastic bag contaminated since it was filled in the contaminated area? Should we disinfect its surface? How? Can we use UV germicidal lamps for this purpose?
A -- Dr. Karen Smith: We know that the virus seems to be able to persist in water for at least a few days in the wild and that, other human influenza viruses can persist for some hours on fomites (objects) in patients' rooms. That said, it is not a particularly hardy virus outside the host. I'm not really sure about UV but see no reason why it would not work. Unlike SARS, influenza (including avian) is not spread by the airborne route, rather it is spread in large droplets. Thus contamination is generally limited to objects within 6 feet or so of the patient. Special decontamination procedures for trash, etc should not be necessary. It is important, however, that persons with direct contact to potentially contaminated items, such as bedding, wear gloves.
Q – Ellena: Shedding virus in high titers in young children could last up to 21 days versus in adults up to 7 days. Is it known why there is such a difference?
A -- Dr. Karen Smith: Interesting question. I don't really know the answer but would hazard a guess that it reflects differences in the pathology of influenza viruses in children vs, adults, perhaps reflecting different immune responses. I do know that the duration of shedding covers quite a range and depends, to some extent, on the severity of the infection.
Q – William: What about industries that use bird products such as feathers for pillows? As an example, in Trinidad, they stopped containers on 21 Nov 2005 of feathers from China used in Carnival costumes.
Do other countries still receive these items?
A -- Dr. Karen Smith: Hmmm, I'm not sure. It depends on what processes are used for disinfection. Given that fowl have large numbers of ecto-parasites that would be found in feathers, I assume some form of disinfection is used. Flu viruses aren't especially robust in the environment and should be killed by most means of disinfection.
A – Gina: What are your recommendations for grounds maintenance workers in terms of PPE in the U.S.? Europe? Southeast Asia?
A -- Dr. Karen Smith: Unless you are referring to workers in the poultry industry, I don't think there are any precautions specific to avian influenza that need to be considered. For poultry workers in flocks where infection is possible, at a minimum, gloves, masks (droplet only), gowns (or some form of clothes and shoe covering), and goggles are used.
Q -- Andrew: Do you have any information on the spread of influenza in an office environment and would you recommend increasing the supply of fresh outdoor air as recommended by ASHRAE?
Reference URL: U.S. EPA Indoor Air Quality Building Education and Assessment guidance (I-BEAM) http://www.epa.gov/iaq/largebldgs/ibeam_page.htm
A -- Dr. Karen Smith: Influenza can and does spread from person to person in pretty much any environment. In usual environments, such as offices, spread is most commonly due to either direct contact with someone shedding the virus (e.g. shaking hands) or use of an inanimate object that has been recently handled by someone shedding virus (e.g. the phone). There is little to no airborne transmission as the droplets in which influenza are spread are quite large and fall out of the air quickly in the area immediately surrounding the person. Ventilation systems are quite good at removing airborne particles (such as TB) but have little effect on larger particles. I doubt changing the ventilation system would have much effect. Interventions designed to increase "social distance" between people are quite effective. Something simple such as staying home when you're sick and using frequent hand washing and covering your mouth when you cough are remarkable effective although admittedly low tech.
Q -- Andrew: Dr. Karen Smith wrote earlier during the Webchat: "Unlike SARS, influenza (including avian) is not spread by the airborne route, rather it is spread in large droplets."
In that case there may not be need to increase the HVAC system ventilation rates in large commercial office buildings. How about "overcrowding"? ASHRAE recommends occupancy rates of 7 persons per 1000 sq. feet of floor space (at fresh outdoor air ventilation rates of 20 cfm per person).
A -- Dr. Karen Smith: I do think overcrowding could be an issue, but only if campaigns to have people stay home when they are sick are ineffective.
Moderator: See: “Food Precautions Necessary To Prevent Bird Flu Transmission” http://usinfo.state.gov/gi/Archive/2005/Nov/10-28826.html
Q – Ellena: Can an infected person shed virus during the incubation period?
If yes, would be there any precautions taken to isolate/quarantine health care workers who handle patients with avian flu?
A -- Dr. Karen Smith: Yes, there is some evidence that influenza viruses can be shed for 1-2 days before symptoms occur. This is most likely in children, however. Also, the amount of virus shed is small compared to the amount shed during the symptomatic period. I'm not sure anyone has ever done a good study to see what contribution virus shedding while asymptomatic makes to the overall spread of influenza during an outbreak.
Moderator: See “Preparing for Pandemic Influenza: What You Can Do?”
Q -- Judy: During what phases of a person being ill with Avian Flu would they be considered contagious and for how long?
A -- Dr. Karen Smith: People are generally considered to be contagious during the time they are shedding live virus particles. There is not a lot of data at this point (because there have been so few cases and they are occurring where sophisticated labs don't exist) on just how long that is. What little data does exist found significant viral loads in nasopharengeal samples 4-8 days after onset of symptoms. I suspect we'll learn more as time goes on and more cases develop. REMEMBER there is NO evidence for transmission of this virus from person to person at this time!
Q -- Micheline: Currently, a strain of the H5 virus has been detected in two ducks from two separate commercial operations in the Fraser Valley area of British Columbia, Canada. Both farms with the infected ducks are undergoing depopulation of the remaining birds, which adds up to over 65,000 ducks. The authorities are culling these birds as a preventative measure, while assuring the public that there is no concern to human health, or to food safety. The infected birds are healthy, suggesting the strain they carry is not dangerous, and so far the strain has affected only ducks, not chickens. The culling is being done to prevent a mutation that could be more dangerous.
More information is available at: http://www.inspection.gc.ca/english/anima/heasan/disemala/avflu/situatione.shtml
A -- Dr. Karen Smith: It's interesting that the authorities chose to cull those flocks as the strain of H5N1 virus that was found there was a known Low Pathogenic H5N1 and NOT the strain of concern from Asia which is a Highly Pathogenic Avian Influenza (HPAI). Despite having the same H and N designations, they are quite different viruses. I was surprised when I read that they were culling as a response to this finding.
Q -- Xia: What precautions, if any, can individuals take when traveling or living in Asia?
A -- Dr. Karen Smith: Avoiding direct exposure to domestic poultry flocks (i.e don't wade through the backyard chickens, ducks or geese at your neighbor's house) is really about the only thing you need to worry about. Making sure any chicken you eat is fully cooked is a good idea for many other reasons as well. There is also some evidence that ingesting infected duck blood (uncooked) may be associated with risk. So you might want to avoid that as well.
Q -- Kara: What breed of birds carry the disease and are capable of spreading the disease to humans?
A -- Dr. Karen Smith: So far, primarily ducks, geese, swans and chickens are the primary types of birds to be affected by the virus (the latter obviously only in domestic flocks). All human cases to date have had exposure to domestic flocks of either chickens or ducks.
Q -- Robert: Are there specific segments in our communities or business here in the US where people may want to take added precautions such as sterilization/air & water filtration in order to better protect themselves or their business?
A -- Dr. Karen Smith:
Not at this time. Should we have a pandemic with many human cases, it will be person-to-person spread that will spread the disease, not water or food. The people who will need to take special precautions are those who care for sick people, those with weakened immune systems, etc.
Moderator: That's all the time we have. Many thanks for participating in today's Webchat on bird flu. Many thanks also to Dr. Smith.
Q -- Andrew:
Dear Dr. Karen Smith,
There is an interesting Power Point Presentation:
Indoor Air Quality in Hong Kong
Central Health Education Unit
DEPARTMENT OF HEALTH
(Distributed by the Bureau of International Information Programs, U.S. Department of State. Web site: http://usinfo.state.gov)
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