Why the bird flu is not passable among humans, not only bird to man?

Question

Why is it bird flu (H5N1), is not passable from human to human, but only between birds and humans? Why can't a person down with the bird flu spread it to other people close to him? After all, the germs emitted from him is in the air.

Sorry, the question should be "Why the bird flu is not passable among humans, only bird to man?"

Answer 1

Avian influenza H5N1 infects the gut of birds because the virus has proteins on it that recognises receptors on bird gut cells.

By some quirck of evolution or the enviroment or what ever, we have the excate same receptors in the bottom of our lungs. For a human to become infected with avian influenza, the virus has to get right down into the lungs, and this is called a Lower Respiratory Tract infection.

Human influenza's infect the Upper respiratory tract, for example, the throat. That is why when we have the flu, and sneeze or cough, we are spreading lots of viruses.

It is possible for human to human spread, and the others are right in saying so. These have come when a sick person has coughed up some virus particles from deep down, but this is hard to do, and doesn't happed very often.

The fear is that the H5N1 might join with a human flu, and change its receptors so that it infects the Upper respiratory tract, and so spread like crazy.

Answer 2

Nemesis is the closest to correct in his answer. There have been cases, documented by the CDC, where it is suspected that the virus was contracted from an infected human. What is most dangerous is the chance that the bird flu may infect a pig for example. Pigs are also susceptible to the human flu virus. Scientist are concerned that the flu virus could breed with the human virus in host susceptible to both and result in a virus that is easily spread from human to human.

I'll spare you a long cut and paste. Try reading the information at:

www.cdc.gov

Answer 3

It is difficult to get it from human to human or bird to human.

It is possible to spread from human to human, but not via the air - like coughing or sneezing. Think of a disease like AIDS - you won't catch that riding on the subway. Sometimes a dangerous flu does come along - see this link on the 1918 version. With so many more people around today and increased mobility, mankind could be hit very hard by an airborne virulent disease.

Answer 4

At present, the bird flu is only capable of passing between birds, and bird to human. In order for the bird flu to pass between humans, it will need to join with the human flu virus and mutate into a new form of bird flu - one which can pass between humans.

Answer 5

Actually there has been human to human transmission but so far only among people living in close quarters. If the virus evolves it may develop a more efficient way of spreading human to human. That's what public health groups are worried about

Answer 6

The chook flu impacts birds because of the fact basically the chook cells have particular receptors on their cellular membranes that enable the virus to attach on, be carried interior, and attack the cellular. The virus can mutate and become able to nicely known receptors on human cells and then attack those cells. If a human comes into touch with a chook with chook flu and the virus gets into the human (many times by way of physique secretions or undesirable hygiene), the virus then has to mutate to stay alive and save on.

Answer 7

Bird flu isn't contagious to humans yet. It's only among birds right now. the worry is that it could become contagious to humans, and that would be a problem, since then we would be passing it among ourselves, and since it is a newer strain, human immunity to it is lower.

Right now, it's nothing to get too worked up over, since we don't know for sure if it will ever be human infective, or if it is, how bad it will be.

Answer 8

if the disease mutates it may well become contagious between humans

Answer 9

Avian Influenza (Bird Flu)
Avian influenza in birds
Avian influenza 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 among birds and can make some domesticated birds, including chickens, ducks, and turkeys, very sick and kill them.

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. Domesticated birds may become infected with 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.

Infection with avian influenza viruses in domestic poultry causes two main forms of disease that are distinguished by low and high extremes of virulence. The “low pathogenic” form may go undetected and usually causes only mild symptoms (such as ruffled feathers and a drop in egg production). However, the highly pathogenic form 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 90-100% often within 48 hours.

Human infection with avian influenza viruses
There are many different subtypes of type A influenza viruses. These subtypes differ because of changes in certain proteins on the surface of the influenza A virus (hemagglutinin [HA] and neuraminidase [NA] proteins). There are 16 known HA subtypes and 9 known NA subtypes of influenza A viruses. Many different combinations of HA and NA proteins are possible. Each combination represents a different subtype. All known subtypes of influenza A viruses can be found in birds.

Usually, “avian influenza virus” refers to influenza A viruses found chiefly in birds, but infections with these viruses can occur in humans. The risk from avian influenza is generally low to most people, because the viruses do not usually infect humans. However, confirmed cases of human infection from several subtypes of avian influenza infection have been reported since 1997. Most cases of avian influenza infection in humans have resulted from contact with infected poultry (e.g., domesticated chicken, ducks, and turkeys) or surfaces contaminated with secretion/excretions from infected birds. The spread of avian influenza viruses from one ill person to another has been reported very rarely, and has been limited, inefficient and unsustained.

“Human influenza virus” usually refers to those subtypes that spread widely among humans. There are only three known A subtypes of influenza viruses (H1N1, H1N2, and H3N2) currently circulating among humans. It is likely that some genetic parts of current human influenza A viruses came from birds originally. Influenza A viruses are constantly changing, and they might adapt over time to infect and spread among humans.

During an outbreak of avian influenza among poultry, there is a possible risk to people who have contact with infected birds or surfaces that have been contaminated with secretions or excretions from infected birds.

Symptoms of avian influenza in humans have ranged from typical human influenza-like symptoms (e.g., fever, cough, sore throat, and muscle aches) to eye infections, pneumonia, severe respiratory diseases (such as acute respiratory distress), and other severe and life-threatening complications. The symptoms of avian influenza may depend on which virus caused the infection.

Studies done in laboratories suggest that some of 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 drugs, so these medications may not always work. Additional studies are needed to demonstrate the effectiveness of these medicines.
Avian Influenza A (H5N1)
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. H5N1 virus does not usually infect people, but infections with these viruses have occurred in humans. Most of these cases have resulted from people having direct or close contact with H5N1-infected poultry or H5N1-contaminated surfaces.

Avian influenza A (H5N1) outbreaks
For current information about avian influenza A (H5N1) outbreaks, see our Outbreaks page.

Human health risks during the H5N1 outbreak
Of the few avian influenza 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. However, it is possible that those cases in the most severely ill people are more likely to be diagnosed and reported, while milder cases go unreported. For the most current information about avian influenza and cumulative case numbers, see the World Health Organization (WHO) avian influenza website.

Of the human cases associated with the ongoing H5N1 outbreaks in poultry and wild birds in Asia and parts of Europe, the Near East and Africa, more than half of those people reported infected with the virus have died. Most cases have occurred in previously healthy children and young adults and have resulted from direct or close contact with H5N1-infected poultry or H5N1-contaminated surfaces. In general, H5N1 remains a very rare disease in people. The H5N1 virus does not infect humans easily, and if a person is infected, it is very difficult for the virus to spread to another person.

While there has been some human-to-human spread of H5N1, it has been limited, inefficient and unsustained. For example, in 2004 in Thailand, probable human-to-human spread in a family resulting from prolonged and very close contact between an ill child and her mother was reported. Most recently, in June 2006, WHO reported evidence of human-to-human spread in Indonesia. In this situation, 8 people in one family were infected. The first family member is thought to have become ill through contact with infected poultry. This person then infected six family members. One of those six people (a child) then infected another family member (his father). No further spread outside of the exposed family was documented or suspected.

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. For more information about influenza pandemics, see PandemicFlu.gov.

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 and widely from person to person.

Treatment and vaccination for H5N1 virus in humans
The H5N1 virus that has caused human illness and death in Asia is resistant to amantadine and rimantadine, two antiviral medications commonly used for influenza. Two other antiviral medications, oseltamavir and zanamavir, would probably work to treat influenza caused by H5N1 virus, but additional studies still need to be done to demonstrate their effectiveness.

There currently is no commercially available vaccine to protect humans against H5N1 virus that is being seen in Asia and Europe. However, vaccine development efforts are taking place. Research studies to test a vaccine to protect humans against H5N1 virus began in April 2005, and a series of clinical trials is under way. For more information about H5N1 vaccine development process, visit the National Institutes of Health website