It is probably not the source of the problem, but it is a factor. The number of studies that compare the prevalence of infectious and chronic diseases between countries is very small.
The thing is, diseases are just like you and me. In general, they’re not all the same. Some are better known, some are worse, but there are people with all kinds of diseases that don’t know what the difference is between them.
Since diseases are similar to our habits, routines, and reactions, a person’s chance of getting sick is largely tied to how many people around them are sick. Not surprisingly, the more people who are sick the more likely you are to get sick, and vice-versa. A very good example of this is the polio epidemic that hit developed countries in the 1920s. The disease was rampant in the US and caused several deaths.
That’s right, when people with polio were traveling around in the late 1920s, there was a lot of sick people in the US. When they returned to their countries the disease was eradicated. When the disease returned there were a lot more people going through it and more people getting sick. Thus the number of people who were sick and the number of people who were not sick increased. It’s called disease transmission.
How do you know this? If you go to a country that has the worst polio, that country is likely to have the highest rate of people who are sick even after the disease is gone.
The polio virus spreads by crossing body fluids, such as sweat, tears, blood and semen. The virus doesn’t live on the body itself, it’s found in a carrier, such as a needle, syringe, syringe cap, or an object used to inject the blood into the body. If a person has the polio virus, they can pass it from person to person, or the body may become infected.
The polio virus also spreads in saliva, the oral mucous membranes. However, the disease is less common there, and the most common route of transmission is oral sex.
So what is it with the polio virus? It certainly appears to be the most common virus causing acute polio, where only about 1-in-10,000,000 persons are positive. Polio has been known to mutate for thousands of years, but the disease has only been seen once or twice in the past century, when a young boy with the disease was discovered in the Netherlands, having symptoms that were similar to what most of us would think of as a cold or flu.
The difference is that polio is considered a viral disease, unlike the common cold, which is caused by a bacteria. In 2013 a study in the U.S. showed a link between polio and a high rate of infertility.
And yes, I know that a virus can cause either a positive or negative effect. But we have to be very careful about how we define a “positive effect.” The negative effects of the common cold are almost always self-limiting, so I guess in that case it makes sense to say that polio causes a positive effect. But in polio epidemics in India, the number of cases go up, so polio may cause a positive effect on the virus.