Questions and answers on bird flu from the CDC.
Influenza A (H5N1) virus--also called H5N1 virus--is an influenza A virus subtype that occurs mainly in birds, is highly contagious among birds, and can be deadly to them.
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 geographically. 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 was reported in Africa and the Near East.
Human cases of influenza A (H5N1) infection have been reported in Azerbaijan, Cambodia, China, Djibouti, Egypt, Indonesia, Iraq, Thailand, Turkey and Vietnam.
What are the risks to humans from the current H5N1 outbreak?
H5N1 virus does not usually infect people, but more than 200 human cases have been reported. Most of these cases have occurred from direct or close contact with infected poultry or contaminated surfaces; however, a few cases of human-to-human spread of H5N1 virus have occurred.
So far, spread of H5N1 virus from person to person has been rare and has not continued beyond one person. Nonetheless, because all influenza viruses have the ability to change, scientists are concerned that H5N1 virus one day could be able to infect humans and spread easily from one person to another. Because these viruses do not commonly infect humans, there is little or no immune protection against them in the human population.
If H5N1 virus were to gain the capacity to spread easily from person to person, an influenza pandemic (worldwide outbreak of disease) could begin. No one can predict when a pandemic might occur. However, experts from around the world are watching the H5N1 situation in Asia and Europe very closely and are preparing for the possibility that the virus may begin to spread more easily from person to person.
How is infection with H5N1 virus in humans treated?
Most H5N1 viruses that have caused human illness and death appear to be resistant to amantadine and rimantadine, two antiviral medications commonly used for treatment of patients with influenza. Two other antiviral medications, oseltamivir and zanamavir, would probably work to treat influenza caused by H5N1 virus, but additional studies are needed to demonstrate their current and ongoing effectiveness.
Is there a vaccine to protect humans from H5N1 virus?
There currently is no commercially available vaccine to protect humans against the H5N1 virus that is being detected in Asia and Europe. However, vaccine development efforts are taking place. Research studies to test a vaccine that will protect humans against H5N1 virus began in April 2005, and a series of clinical trials is under way.
Does CDC recommend travel restrictions to areas with known H5N1 outbreaks?
CDC does not recommend any travel restrictions to affected countries at this time. However, CDC currently advises that travelers to countries with known outbreaks of H5N1 influenza avoid poultry farms, contact with animals in live food markets and any surfaces that appear to be contaminated with feces from poultry or other animals.
Is there a risk in handling feather products that come from countries experiencing outbreaks of avian influenza A (H5N1)?
The U.S. government has determined that there is a risk to handling feather products from countries experiencing outbreaks of H5N1 influenza.
There is currently a ban on the importation of birds and bird products from H5N1-affected countries in Africa, Asia and Europe. The regulation states that no person may import or attempt to import any birds (Class Ayes), whether dead or alive, or any products derived from birds (including hatching eggs), from the specied countries. This prohibition does not apply to any person who imports or attempts to import products derived from birds if, as determined by federal officials, such products have been properly processed to render them noninfectious so that they pose no risk of transmitting or carrying H5N1 and which comply with the U.S. Department of Agriculture (USDA) requirements. Therefore, feathers from these countries are banned unless they have been processed to render them noninfectious.
Is there a risk to importing pet birds that come from countries experiencing outbreaks of avian influenza A (H5N1)?
The U.S. government has determined that there is a risk to importing pet birds from countries experiencing outbreaks of H5N1 influenza. CDC and USDA have both taken action to ban the importation of birds from areas where H5N1 has been documented.
Can a person become infected with avian influenza A (H5N1) virus by cleaning a bird feeder?
There is no evidence of H5N1 having caused disease in birds or people in the United States. At the present time, there is no risk of becoming infected with H5N1 virus from bird feeders. Generally, perching birds (Passeriformes) are the predominate type of birds at feeders. While there are documented cases of H5N1 causing death in some Passeriformes (e.g., house sparrow, Eurasian tree-sparrow, house finch), in both free-ranging and experimental settings, none occurred in the United States and most of the wild birds that are traditionally associated with avian influenza viruses are waterfowl and shore birds.
INFLUENZA PANDEMIC PREPAREDNESS
What changes are needed for H5N1 or another avian influenza virus to cause a pandemic?
Three conditions must be met for a pandemic to start: 1) a new influenza virus subtype must emerge for which there is little or no human immunity; 2) it must infect humans and causes illness; and 3) it must spread easily and sustainably (continue without interruption) among humans. The H5N1 virus in Asia and Europe meets the first two conditions: it is a new virus for humans (H5N1 viruses have never circulated widely among people), and it has infected more than 190 humans, killing over half of them.
However, the third condition, the establishment of efficient and sustained human-to-human transmission of the virus, has not occurred. For this to take place, the H5N1 virus would need to improve its transmissibility among humans. This could occur either by "reassortment" or adaptive mutation.
Reassortment occurs when genetic material is exchanged between human and avian viruses during co-infection (infection with both viruses at the same time) of a human or another mammal. The result could be a fully transmissible pandemic virus--that is, a virus that can spread easily and directly between humans. A more gradual process is adaptive mutation, where the capability of a virus to bind to human cells increases during infections of humans.
AVIAN FLU AND HUMAN HEALTH
How is avian influenza detected in humans?
Avian influenza cannot be diagnosed by symptoms alone, so a laboratory test is required. Avian influenza is usually diagnosed by collecting a swab from the nose or throat during the first few days of illness. This swab is then sent to a laboratory, where they will either look for avian influenza virus using a molecular test, or they will try to grow the virus. Growing avian influenza viruses should only be done in laboratories with high levels of protection. If it is late in the illness, it may be difficult to find an avian influenza virus directly using these methods. If this is the case, it may still be possible to diagnose avian influenza by looking for evidence of the body's response to the virus. This is not always an option because it requires two blood specimens (one taken during the first few days of illness and another taken some weeks later), and it can take several weeks to verify the results.
What are the implications of avian influenza to human health?
Two main risks for human health from avian influenza are 1) the risk of direct infection when the virus passes from the infected bird to humans, sometimes resulting in severe disease; and 2) 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.
How is avian influenza in humans treated?
Studies done in laboratories suggest that the prescription medicines approved for human influenza viruses should work in treating avian influenza infection in humans.
However, influenza viruses can become resistant to these drugs, so these medications may not always work. Additional studies are needed to determine the effectiveness of these medicines.
Does seasonal influenza vaccine protect against avian influenza infection in people?
No. Seasonal influenza vaccine does not provide protection against avian influenza.
Should I wear a surgical mask to prevent exposure to avian influenza?
Currently, wearing a mask is not recommended for routine use (e.g., in public) for preventing influenza exposure. In the United States, disposable surgical and procedure masks have been widely used in health-care 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.
Can I get avian influenza from eating or preparing poultry or eggs?
You cannot get avian influenza from properly handled and cooked poultry and eggs.
There currently is no scientific evidence that people have been infected with bird flu by eating safely handled and properly cooked poultry or eggs.
Most cases of avian influenza infection in humans have resulted from direct or close contact with infected poultry or surfaces contaminated with secretions and excretions from infected birds. Even if poultry and eggs were to be contaminated with the virus, proper cooking would kill it. In fact, recent studies have shown that the cooking methods that are already recommended by the U.S. Department of Agriculture (USDA) and the Food and Drug Administration (FDA) for poultry and eggs to prevent other infections will destroy influenza viruses as well.
So to stay safe, the advice is the same for protecting against any infection from poultry:
* Wash your hands with soap and warm water for at least 20 seconds before and after handling raw poultry and eggs.
* Clean cutting boards and other utensils with soap and hot water to keep raw poultry from contaminating other foods.
* Use a food thermometer to make sure you cook poultry to a temperature of at least 165 degrees Fahrenheit. Consumers may wish to cook poultry to a higher temperature for personal preference.
* Cook eggs until whites and yolks are firm.
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 still is in place.
We have a small flock of chickens. Is it safe to keep them?
Yes. In the United States there is no need at present to remove a flock of chickens because of concerns regarding avian influenza. The U.S. Department of Agriculture monitors potential infection of poultry and poultry products by avian influenza viruses and other infectious disease agents.
AVIAN INFLUENZA IN ANIMALS
What animals can be infected with avian influenza A (H5N1) viruses?
In addition to humans and birds, we know that pigs, tigers, leopards, ferrets and domestic cats can be infected with avian influenza A (H5N1) viruses. In addition, in early March 2006, Germany reported H5N1 infection in a stone marten (a weasel-like mammal). The avian influenza A (H5N1) virus that emerged in Asia in 2003 is evolving and it's possible that other mammals may be susceptible to infection as well. CDC is working closely with domestic and international partners to continually monitor this situation and will provide additional information to the public as it becomes available.
Can domestic cats be infected with avian influenza viruses?
While domestic cats are not usually susceptible to influenza type A infection, it is known that they can become infected and die (both experimentally and naturally) with avian influenza A (H5N1) viruses and, in a laboratory/research setting can spread the virus to other cats.
It is not known whether domestic cats can spread the virus to other domestic cats under natural conditions.
How do cats become infected with avian influenza A (H5N1) viruses?
All of the cases of influenza A (H5N1) infection in domestic cats reported to date have been associated with H5N1 outbreaks among domestic poultry or wild birds and are thought to have occurred by the cat eating raw infected birds.
How commonly have cats been infected with avian influenza A (H5N1) viruses?
During the avian influenza A (H5N1) outbreak that occurred from 2003 to 2004 in Asia, there were only several unofficial reports of fatal infections in domestic cats.
Studies carried out in the Netherlands and published in 2004 showed that housecats could be infected with avian influenza A (H5N1) and could spread the virus to other housecats. In these experiments, the cats became sick after direct inoculation of virus isolated from a fatal human case, and following the feeding of infected raw chicken.
In February 2006, Germany reported that a domestic cat had died from influenza A (H5N1) infection. That cat lived in the northern island of Ruegen, where more than 100 wild birds are believed to have died of the disease. The cat probably got sick by eating an infected bird.
Can cats spread H5N1 to people?
There is no evidence to date that cats can spread H5N1 to humans. No cases of avian influenza in humans have been linked to exposure to sick cats, and no outbreaks among populations of cats have been reported.
What is the current risk that a cat in the United States will become infected with influenza A (H5N1) ?
As long as there is no influenza A (H5N1) in the United States, there is no risk of a U.S. cat becoming infected with this disease. The virus circulating in Asia, Europe and Africa has not yet entered the United States.
Can dogs be infected with avian influenza?
While dogs are not usually susceptible to avian influenza viruses, the avian influenza A (H5N1) virus that emerged in Asia in 2003 has been documented to infect other carnivore species (e.g. cats, tigers, leopards, stone martens). This has raised concern that this strain of avian influenza A (H5N1) virus may be capable of infecting dogs. An unpublished study carried out in 2005 by the National Institute of Animal Health in Bangkok indicated that dogs could be infected with the virus, but no associated disease was detected. This limited information is not enough to determine definitively whether dogs are susceptible to the virus.
Questions and Answers on Bird Flu from the World Health Organization
What is avian influenza?
Avian influenza, or "bird flu," is a contagious disease of animals caused by viruses that normally infect only birds and, less commonly, pigs. Avian influenza viruses are highly species-specific, but have, on rare occasions, crossed the species barrier to infect humans.
In domestic poultry, infection with avian influenza viruses causes two main forms of disease, distinguished by low and high extremes of virulence. The so-called "low pathogenic" form commonly causes only mild symptoms (ruffled feathers, a drop in egg production) and may easily go undetected. The highly pathogenic form is far more dramatic. It spreads very rapidly through poultry flocks, causes disease affecting multiple internal organs, and has a mortality that can approach 100 percent, often within 48 hours.
Which viruses cause highly pathogenic disease?
Influenza A viruses have 16 H subtypes and 9 N subtypes. Only viruses of the H5 and H7 subtypes are known to cause the highly pathogenic form of the disease. However, not all viruses of the H5 and H7 subtypes are highly pathogenic and not all will cause severe disease in poultry.
On present understanding, H5 and H7 viruses are introduced to poultry flocks in their low pathogenic form. When allowed to circulate in poultry populations, the viruses can mutate, usually within a few months, into the highly pathogenic form. This is why the presence of an H5 or H7 virus in poultry is always cause for concern, even when the initial signs of infection are mild.
What is special about the current outbreaks in poultry?
The current outbreaks of highly pathogenic avian influenza, which began in South-East Asia in mid-2003, are the largest and most severe on record. Never before in the history of this disease have so many countries been simultaneously affected, resulting in the loss of so many birds.
The causative agent, the H5N1 virus, has proved to be especially tenacious. Despite the death or destruction of an estimated 150 million birds, the virus is now considered endemic in many parts of Indonesia and Vietnam and in some parts of Cambodia, China, Thailand, and possibly also the Lao People's Democratic Republic. Control of the disease in poultry is expected to take several years.
Why are pandemics such dreaded events?
Influenza pandemics are remarkable events that can rapidly infect virtually all countries. Once international spread begins, pandemics are considered unstoppable, caused as they are by a virus that spreads very rapidly by coughing or sneezing. The fact that infected people can shed virus before symptoms appear adds to the risk of international spread via asymptomatic air travellers.
The severity of disease and the number of deaths caused by a pandemic virus vary greatly and cannot be known prior to the emergence of the virus. During past pandemics, attack rates reached 25-35 percent of the total population. Under the best circumstances, assuming that the new virus causes mild disease, the world could still experience an estimated 2 million to 7.4 million deaths (projected from data obtained during the 1957 pandemic). Projections for a more virulent virus are much higher. The 1918 pandemic, which was exceptional, killed at least 40 million people. In the USA, the mortality rate during that pandemic was around 2.5 percent.
Pandemics can cause large surges in the numbers of people requiring or seeking medical or hospital treatment, temporarily overwhelming health services. High rates of worker absenteeism can also interrupt other essential services, such as law enforcement, transportation, and communications. Because populations will be fully susceptible to an H5N1-like virus, rates of illness could peak fairly rapidly within a given community. This means that local social and economic disruptions may be temporary. They may, however, be amplified in today's losely interrelated and interdependent systems of trade and commerce. Based on past experience, a second wave of global spread should be anticipated within a year.
As all countries are likely to experience emergency conditions during a pandemic, opportunities for inter-country assistance, as seen during natural disasters or localized disease outbreaks, may be curtailed once international spread has begun and governments focus on protecting domestic populations.
What are the most important warning signals that a pandemic is about to start?
The most important warning signal comes when clusters of patients with clinical symptoms of influenza, closely related in time and place, are detected, as this suggests human-to-human transmission is taking place. For similar reasons, the detection of cases in health workers caring for H5N1 patients would suggest human-to-human transmission. Detection of such events should be followed by immediate field investigation of every possible case to confirm the diagnosis, identify the source, and determine whether human-to-human transmission is occurring.
Studies of viruses, conducted by specialized WHO reference laboratories, can corroborate field investigations by spotting genetic and other changes in the virus indicative of an improved ability to infect humans. This is why WHO repeatedly asks affected countries to share viruses with the international research community.
What is the status of vaccine development and production?
Vaccines effective against a pandemic virus are not yet available. Vaccines are produced each year for seasonal influenza but will not protect against pandemic influenza. Although a vaccine against the H5N1 virus is under development in several countries, no vaccine is ready for commercial production and no vaccines are expected to be widely available until several months after the start of a pandemic.
Some clinical trials are now under way to test whether experimental vaccines will be fully protective and to determine whether different formulations can economize on the amount of antigen required, thus boosting production capacity. Because the vaccine needs to closely match the pandemic virus, large-scale commercial production will not start until the new virus has emerged and a pandemic has been declared. Current global production capacity falls far short of the demand expected during a pandemic.
Can a pandemic be prevented?
No one knows with certainty. The best way to prevent a pandemic would be to eliminate the virus from birds, but it has become increasingly doubtful if this can be achieved within the near future.
Following a donation by industry, WHO will have a stockpile of antiviral medications, sufficient for 3 million treatment courses, by early 2006. Recent studies, based on mathematical modelling, suggest that these drugs could be used prophylactically near the start of a pandemic to reduce the risk that a fully transmissible virus will emerge or at least to delay its international spread, thus gaining time to augment vaccine supplies.
The success of this strategy, which has never been tested, depends on several assumptions about the early behaviour of a pandemic virus, which cannot be known in advance.
Success also depends on excellent surveillance and logistics capacity in the initially affected areas, combined with an ability to enforce movement restrictions in and out of the affected area.
To increase the likelihood that early intervention using the WHO rapid-intervention stockpile of antiviral drugs will be successful, surveillance in affected countries needs to improve, particularly concerning the capacity to detect clusters of cases closely related in time and place.
This set of questions and answers is drawn from the World Health Organization's (WHO's) frequently asked questions on avian flu. WHO maintains a web page on avian flu at: <www.who.int/csr/disease/avian_influenza/en/index.html>.
Pandemic Flu Planning Checklist for Individuals and Families
You can prepare for an influenza pandemic now. You should know both the magnitude of what can happen during a pandemic outbreak and what actions you can take to help lessen the impact of an influenza pandemic on you and your family. This checklist will help you gather the information and resources you may need in case of a flu pandemic.
1. To plan for a pandemic:
* Store a two-week supply of water and food. During a pandemic, if you cannot get to a store, or if stores are out of supplies, it will be important for you to have extra supplies on hand. This can be useful in other types of emergencies, such as power outages and disasters.
* Have any nonprescription drugs and other health supplies on hand, including pain relievers, stomach remedies, cough and cold medicines, fluids with electrolytes and vitamins.
* Talk with family members and loved ones about how they would be cared for if they got sick, or what will be needed to care for them in your home.
* Volunteer with local groups to prepare and assist with emergency response.
* Get involved in your community as it works to prepare for an influenza pandemic.
2. To limit the spread of germs and prevent infection:
* Teach your children to wash hands frequently with soap and water, and model the correct behavior.
* Teach your children to cover coughs and sneezes with tissues, and be sure to model that behavior.
* Teach your children to stay away from others as much as possible if they are sick. Stay home from work and school if sick.
3. Items to have on hand for an extended stay at home:
* Examples of food and non-perishables:
Ready-to-eat canned meats, fish, fruits, vegetables, beans, and soups; protein or fruit bars; dry cereal or granola; peanut butter or nuts: dried fruit; crackers; canned juices; bottled water; canned or jarred baby food and formula; pet food; other non-perishable items.
* Examples of medical, health, and emergency supplies: prescribed medical supplies such as glucose and blood-pressure monitoring equipment; soap and water, or alcohol-based (60-95 percent) hand wash; medicines for fever, such as acetaminophen or ibuprofen; thermometer; anti-diarrheal medication; vitamins; fluids with electrolytes; cleansing agent/soap; flashlight; batteries; portable radio; manual can opener; garbage bags; tissues, toilet paper, disposable diapers.
Source: This checklist is provided by the U.S. Department of Health and Human Services, which maintains a website on avian and pandemic flu at <www.pandemicflu.gov>.
This set of questions and answers is drawn from the U.S. Centers for Disease Control (CDC) frequently asked questions on avian flu. The CDC maintain a web page on avaian flu at: <www.cdc.gov/flu/avian/index.htm>.
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|Title Annotation:||QUESTIONS & ANSWERS ON BIRD FLU; Centers for Disease Control and Prevention|
|Date:||Mar 1, 2006|
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