Flu epidemics can travel rapidly through the population. It seems as if there is a new epidemic predicted every year and new strains of the virus appear regularly. If you watch the news, it seems that these epidemics usually start in Asia.
Q: Do flu epidemics really start in Asia, and if so, why does this happen?
A: Avian flu viruses occur naturally in bird populations around the world. Although wild birds carry the viruses, they usually do not get sick from them. The viruses are very contagious, though, and domestic birds, such as chickens, ducks, and turkeys can contract flu from the wild birds.
Mutations in viruses and transfer of DNA among them can occur at any place in the world. So why do so many of them seem to come from Asia? For viruses related to birds and other farm animals, part of the reason may be related to differences in farming around the world. In Europe and North America, poultry are generally raised in large farms. In much of the rural parts of Asia, though, most households have some chickens, ducks, or other birds that provide eggs and meat. Therefore, a much larger part of the population has close contact with domestic birds. Another reason that Asia is often a source of flu viruses may be even more basic. A very large percentage of the world’s population lives in Asia. That means there are a lot more people who could be the original host to a mutated virus.
Q: So, what exactly is the flu?
A: Influenza, or flu, is caused by a virus that works its way into cells and takes over. Then, instead of operating normally, the cells begin to produce new viruses, which attack more cells. Many of the uncomfortable symptoms of flu occur as your body fires up the immune system to fight the invasion. Other symptoms—such as coughing, sneezing, and lung congestion—occur as dead cells, killed by the virus invasion, accumulate in tissues.
Generally, after your body has fought a virus once, the immune system “remembers” it and delivers a knockout blow quickly when the next invasion starts. Sometimes though, a small change in the virus structure can hide it from the system. Then your body has to learn to fight it all over again.
Q: Why are they so dangerous?
A: One of the reasons that flu can become such a problem is that there are many different strains of the virus. Some of them infect only people. Others infect animals such as birds, horses, and pigs. Normally these viruses are not a problem for people. However, viruses occasionally mutate and gain the ability to pass from one species to another. Influenza viruses have eight segments of genetic material, two of which determine whether the virus is able to infect a particular type of host. Viruses are able to swap genes with one another, so if human and animal viruses come together, a new virus can form.
It may all sound scary, but the best defense against the flu is knowledge—and vaccination. Although vaccines won’t rule out every single variation of the flu, they can protect you from the ones that are most virulent. Stay safe!
From The Complete Idiot’s Guide to the Science of Everything by Steve Miller