When a natural disaster wipes out power for a large area, it wipes out our access to nearly every resource. Imagine an EMP on a global or even a country-sized level, and our biggest concerns will not be starving to death; we'll die of disease long before that ever happens.

WATER
One of the first things to go, regardless of the cause of collapse, may be access to clean water. Bacterial infections (such as cholera, dysentery, and typhoid), protozoan infections (such as giardia and cryptosporidiosis), parasitic infections (such as schistosomiasis), and viral infections (such as polio and hepatitis A) will arise primarily due to fecal matter in the water, and even water from the most pristine high-altitude streams will not be safe to drink without treatment. In the emergency preparedness classes that I taught, I collected water from a scummy pond. With an abundance of algae, it was very green and contained a lot of solid matter. I made for samples for demonstration purposes: 1) passed only through a coffee filter; 2) boiled; 3) distilled; 4) treated with bleach. Without revealing the treatment methods used, I asked the class which water looked best and safest to drink. Hands down, everyone chose the clearest, cleanest, purest looking sample—the water that was only passed through a coffee filter. The boiled, distilled, and bleach-treated samples were all off in color. It was at that point I realized that once the collapse begins, we need to be prepared to purify all of our water ourselves, and not rely on anyone else.
FOOD
While illnesses arising from impure water will start quickly after collapse beings, increases in cases of food poisoning won’t be far behind. There is a wide variety of bacteria that cause food-borne illnesses. Some will only cause vomiting and/or diarrhea; others can be fatal. Of course, that is the case even now, when all is apparently well in our world. However, when people become desperate due to dwindling food supplies, they will also start eating food they normally would have tossed out. And they may become less cautious about the hygiene standards for those preparing the food.
MOSQUITOES
Mosquitoes can carry bacteria, viruses, and parasites, making them an efficient vector for the transmission of dozens of diseases. While they pose a much greater threat in tropic and subtropical climates, mosquitoes range throughout North America. The most serious diseases spread by mosquitoes in North America at this time are western equine encephalitis and eastern equine encephalitis. However, in a grid-down situation, where municipalities are no longer actively combating mosquitoes and when filters and chemicals for backyard swimming pools are no longer being used, the mosquito population will increase astronomically—as will the number of diseases and cases. The incidence of malaria and yellow fever will definitely surge, as also will in all likelihood cases of zika, chikungunya, and dengue. To reduce chances for mosquito bites, wear clothing that fully covers the skin, eliminate open sources of water, utilize window screens and mosquito netting where possible, and apply mosquito repellents to exposed skin.
ACCIDENTAL INJURIES
As the society we have been raised in regresses to the 1800’s, as access to unlimited amounts of clean water and quality food decreases, and as people start working more physically, the number of accidental wounds and injuries will increase. As good nutrition decreases, the ability of the body to fight minor infections will also decrease. Simple scratches, even hangnails, will have the potential to become life-threatening.
COMMUNICABLE DISEASES
Careful hand-washing and avoiding crowds will go a long ways towards avoiding infection, as will keeping current on vaccinations. For those illnesses that breach your defenses, make sure you have an area that can be used for quarantine.
VERMIN
While lice and bedbugs don’t necessarily transmit disease (they may), they do make people uncomfortable with either the itching or the mere thought of their possible presence. Don’t share personal items such as combs, brushes, sheets, or towels. As with most diseases, prevention is easier than treatment.
MALNUTRITION
As the new normal lingers, malnutrition will become increasingly common. As a group, we have a reputation for having gathered and stored food to see us through to the other side. However, we can’t store food for everyone and we need to be prepared to improvise if for whatever reason our supplies run out.
Most nutritionists agree that a ratio of 40% carbohydrates, 30% protein, and 30% fats is healthy. However, what we actually consume varies widely, with women more likely to consume more carbohydrates and less protein, and the opposite for men. When the grid goes down, we’re going to be spending more time in physical labor, and our caloric and nutritional demands will change, sometimes drastically. And sometimes, people will have to make do with what they can find for food.
The symptoms of protein deficiency are varied and non-specific and include weakness, fatigue, and reduced immune system function. Symptoms of carbohydrate deficiency are similar to those for protein deficiency but also include depression and mood swings. Symptoms of fat deficiency (which can occur even on overweight individuals) are similar to those of carbohydrate deficiency but also include reduced brain function and an increase in skin problems. And fats are essential for the body to be able to absorb the fat-soluble vitamins A, D, and E.
In the developed world we have been blessed for so long to have ready access to a widely varied diet that we have not seen manifest the effects of vitamin deficiencies for the most part, or at least those deficiencies due entirely to diet alone. Even when things fall apart, it will be a long time before we see problems with vitamin A and B deficiencies. When we run out of fresh or preserved fruits, problems with vitamin C deficiencies will likely arise. Teas can be made from pine needles or rose hips, or juice can be made from wheat grass to provide this essential vitamin. Vitamin D occurs naturally in only a few foods—generally fish and eggs. When these dietary options become limited, just make sure to get at least a few minutes of sun each day, exposing as much of the skin as reasonably possible, and without sunscreen.
As variety in the diet and as food in general become restricted, conditions caused by dietary mineral deficiencies will present themselves. The best prevention will be raising your own vegetables and fruits and including whole grains and beans in your diet. Add in some eggs from your flock of chickens and use iodized salt and you’ll be well covered.

Malnutrition is the last concern on the list because it implies that we'll be able to sort everything else out. Unfortunately, millions of people will die before that happens. Clean water and maintaining a clean living environment will be the most valuable aspects of that society, and not doing so will result in a horrifying look into the world before the advent of soap and modern medicine. In this case, its stock up on everything you need today so you won't die of a hangnail tomorrow.

This is a wake-up call for those who are only concerned with stocking up on guns, ammo, and food. For more information on this topic, take a look at the original article at The Prepper Journal.