Antiviral drugs are a major new area of pharmaceutical investigation, one with a lot of promise. Viruses are very difficult to kill effectively without harming the host. This is related to how they reproduce. Unlike bacteria, which are prokaryotic cells that live and reproduce on their own inside the body, viruses are not really alive at all. Rather, they are little more than a few strands of RNA or DNA enclosed in a protein capsule. In order to reproduce they must invade a cell and take over its cellular machinery, forcing the cell to produce more viruses. This makes it very difficult to kill. With bacteria, scientists are able to discover or make drugs that effectively kill the bacterial cells without hurting the human cells. This is possible because in some ways the bacterial cells are very different from the human cells, so the drugs can affect the bacteria without affecting the human. With viruses, though, this approach doesn't really work. Before viruses invade a cell they aren't even really alive, and how can you kill something that isn't even alive? After they invade the cell, they become a part of the cell, so anything that will hurt the virus-occupied cell will also hurt the normal cells, and therefore the drug could kill you while it was killing the viruses!
Because of this, we have had antibiotic drugs to kill bacteria for over eighty years now, but effective antiviral medications have only begun to show up on the market in the past 15 years. However, this shows that scientists are finally beginning to figure out ways of stopping viruses, and they are discovering more effective methods all the time. One trick that they can use, for example, is to give a patient a drug that makes it hard to make copies of DNA from RNA. This way when a virus tries to force the cell to produce DNA from viral RNA, the cell can't really do it. This could, of course, hurt some normal cellular processes that also require making DNA from RNA, but it will hurt the virus-infected cells way more since the viruses need to do this a lot more than normal cells do.
Most antiviral drugs work in this type of fashion: the drug will probably affect all of your cells, but it will affect the virus-infected cells way more, so that at least there aren't any new viruses being produced. (How much a drug affects the virus compared to your normal cells depends on how the drug works, some are very specific to the virus and others are more generally acting). Then, your own body's immune defenses can do the rest, killing the viruses that are already there. The drugs really help your immune system by slowing down the virus reproduction so your immune system can keep up with the viruses. Just like antibiotics for bacteria, antivirus drugs do work in different ways though and therefore are more or less effective against different types of viruses. So, some antiviral drugs may prove to be very effective against the bird flu, and others may not be very effective at all.
You are right: antiviral medications are very similar to antibiotics against bacteria in that you would indeed have to keep taking the drug to suppress the viruses until the threat is gone, and the drug will not give you immunity.
One major additional problem with these antiviral drugs that is different from how things work with antibiotics is that they really only prevent virus reproduction-- they don't actually kill the viruses that are already there. This is a big problem because many viruses are latent. This means they will occupy a cell, but they will just stay there dormant for a while, not really doing anything. The antiviral drugs will not get rid of these latent viruses. So, lets say you get sick with a virus, and you begin to take the antiviral drugs. Together with your immune system the drugs do a good job to make you feel better, and your body isn't full of viruses anymore. However, you may still have the virus inside some of your cells, just hanging out. Then, one day after you've stopped taking the drugs, the virus can wake up and become active again, producing more viruses without being stopped by the drug since you have quit taking it. However, then if you start feeling sick again you can always start taking the drug again. So the drugs, while not perfect, are still a good solution, and are certainly better than just letting the virus make you sick if the virus is a dangerous one! It is a treatment, but not a cure.
For this reason, a virus vaccine is a much better option. Your immune system is a complicated defense system that is capable of learning how to recognize invaders. Once your immune system knows how to recognize an invader that shouldn't be there, it can mount an attack against it.
Those are all good questions. Some information on this was published in February 2005. Basically, it's hard to tell how well the newest anti-viral drugs will work against avian influenza since they are not widely available in Asia, where most of the cases have been. Understandably, you can't do experiments on humans to test this, so you can only rely on hospital records from patients with confirmed cases of H1N5 (many hospitals in Asia don't have the capability to accurately I.D. strains of influenza) AND where anti-viral drugs are available (again, most hospitals in Asia only have access to older anti-viral drugs, to which viruses have become widely resistant).
Using this method, scientists have gathered some data on how effective certain antiviral drugs are against H1N5 in a few cases. The answer appears to be that they are not very effective. The results are a little unclear, though, since the culture in Asia is so different. People are less likely to go hospitals or clinics in rural China, Vietnam and Thailand to get care when they first show symptoms. So most of the people that ended up at hospitals with confirmed cases of H1N5 were very sick. Antiviral agents work best when they are taken early in the disease so the fact that the drugs weren't very effective against H1N5 in these patients may not mean much. For this reason, scientists working with the World Health Organization have set up small clinics around Asia in towns where H1N5 outbreaks have occurred, or where poultry farms are common. They are also trying to educate the public about the disease (symptoms, e.g.) and encourage them to visit the clinics as soon as they get sick with any cold or flu-like symptoms. The clinics are staffed with equipment to I.D. influenza strains and are stocked with some anti-viral drugs. Analyzing the results will take time.
As far as loading up on anti-viral drugs to protect yourself from H1N5, this is equivalent to loading up on antibiotics to protect yourself from bacterial infection. It's a VERY bad idea. First of all, the drugs are expensive. We don't know if they'll actually work. If enough people in developed countries start stock-piling the drugs, less will be available in Asia and other countries where they're needed. And most importantly, viruses mutate quickly and easily become resistant to anti-viral drugs (AIDS patients know this well). So if everyone runs around taking these drugs, they are exposing themselves to side effects from the drugs and at the same time making all viruses that much more resistant. And yes, you would have to take the drugs until a reliable vaccine is developed to stay "protected". There are vaccines against influenza (the flu shot), but there are so many strains of influenza and they mutate so quickly that we can't vaccinate everyone against them all. This is why the flu shot changes every year. It's a guess based on world-wide data about which three influenza strains will be the most common that year.
I can assure you scientists are currently working on a vaccine for H1N5. This requires that we isolate the virus (done), determine the most effective type of vaccine andtest it (currently being done), and finally that a drug company manufactures it for world-wide distribution. I'm guessing that when an H1N5 vaccine becomes available, it will be necessary to get the shot every year. Influenza mutates very quickly (like AIDS), so vaccines won't be able to give you long-term immunity. I don't see drug companies making it available in the US until (1) we get confirmed cases of avian influenza in the US and (2) the virus mutates enough to spread by human-to-human contact.
Currently, the only way you can get the H1N5 flu is from direct contact with a sick bird or possibly by eating the meat of a sick bird.
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