Disease #1: Rabies
Rabies is a virus that is spread mostly through animal bites. Specifically if the animal is rabid and bites, to puncture your skin and draw blood, is when you'd most likely contract the virus. A more rare way to get infected is through skin abrasions, cuts and scratches, or rabid animal saliva coming into contact with an open wound.
To slow the spread of rabies, vaccinations are very important. A vaccine is basically a weakened virus (one that isn't as deadly/infectious as its wild counterpart) that trains your immune system in knowing how to combat the virus. With vaccinations, the rabies virus doesn't spread as much, and therefore it cannot get out of control. Vaccinations in this case would be for both people and animals. Another way to control the rabies virus is through proper methods of animal control. Animal control is critical in keeping sick animals away from human populations, and also to help cure the disease in those animals.
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Disease #2: Malaria
This disease comes about from mosquito bites. Specifically, there is a very small parasite in the mosquito that makes people very ill if the parasite attaches onto the human. Symptoms include having fevers and chills as outward signs, but inside the body, the parasite destroys red blood cells and makes it nearly impossible for the body to make more. The lack of oxygen that results is what usually kills people. Thankfully treatment is possible. One such treatment is called Quinine.
The best way to treat malaria is to prevent it completely. This is through the use of proper mosquito netting to keep bugs out, and elimination of standing water to prevent mosquitoes laying eggs to hatch new ones. Standing water is simply any pool/puddle of water that does not move. If the water did move, then it would carry the eggs downstream and perhaps destroy the larvae. Pesticides are another option, though it is ideal to use chemicals that aren't harmful to the environment/plants/people.
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Disease #3: Cholera
Whenever you have bacterial infection of food and/or water, then chances are it might be Cholera that is to blame. This was very common in days when clean water was hard/expensive to come by, so deaths were tragically fairly high. Through advances in technology, developed countries take for granted that Cholera is essentially the thing of the past (at least for the developed countries I mean). The disease is really rare these days (about 1000 cases per year)
Treating Cholera involves antibiotics to prevent the bacteria from spreading. Patients also must make sure to get plenty of fluids of water and other electrolytes (often through intravenous tubes). Like with the other two diseases, prevention is a much smarter route. Having clean water will help stop the spread of Cholera.
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For each disease mentioned, the act of treatments and prevention are all methods to interrupt the flow of the diseases. Without any of these tools to keep the disease in check, it would most likely cause major damage on the human population.
