I believe the fourth horse has begun to ride, and we will soon see death from famine in countries that have never experience famine. Another means of death mentioned in the verse below is the "beasts of the earth".
Rev 6:8 And I looked, and behold a pale horse: and his name that sat on him was Death, and Hell followed with him. And power was given unto them over the fourth part of the earth, to kill with sword, and with hunger, and with death, and with the beasts of the earth.
For many years whenever I read this I couldn't really see how the beasts of the earth would be killing people. Was it talking about some of the kinds of things seen in some of those "B" movies featuring certains animals, snakes or insects killing every human unfortunate enough to get in their way? Movies that showed frogs, ants, snakes, spiders and even rabbits running amok, usually as a result of human stupidity.
Here's a list of just some of the diseases that could easily go out of control, all transmitted by some member of the animal kingdom.
Bird flu: H5N1 infections are becoming the rule rather then the exception in farmed poultry worldwide, and even wild birds are showing signs of infection more often. It has forced the culling of millions of ducks, chickens and geese globally—and has killed more than 240 people—resulting in at least $100 billion in economic losses.
Babesiosis: This malarialike disease carried by ticks is endemic in the tropics, but has cropped up everywhere from Italy to Long Island, N.Y. It is rare in humans at present and seldom deadly (treatable with antibiotics) but may become more problematic as the globe warms, providing more welcoming environments.
Cholera: This bacterium thrives in warmer waters and causes diarrhea so severe that it can kill within a week. Without improved sanitation, rising global temperatures will increase deadly outbreaks.
Ebola: This virus is lethal to humans and other primates, and has no cure. In addition, it is unclear where the disease, which causes fever, vomiting and internal or external bleeding, comes from—though scientists suspect fruit bats. What is clear is that outbreaks tend to follow unusual downpours or droughts in central Africa—a likely result of climate change.
Parasites: Many spread easily between humans, livestock and wildlife. Higher average temperatures and more rainfall will help many parasites, such as the tiny worms known as Baylisascaris procyonis that are spread by raccoons, to thrive in the wild before finding a host.
Lyme disease: This bacterium-caused disease will spread as climate changes extend the ranges of the ticks that carry it.
Plague: Changes in temperature and rainfall will affect rodent populations globally as well as the infected fleas they carry.
"Red tides": Poisonous algal blooms in coastal waters may increase as a result of warming temperatures or changes in littoral sea life.
Rift Valley fever: A newly emergent virus, carried by mosquitoes that causes fever and weakness, has spread quickly through Africa and the Middle East, killing people, along with camels, cattle, goats and sheep.
Sleeping sickness: Global warming will change the distribution of the tsetse fly that carries the disease, now infecting more than 300,000 people yearly in Africa. Victims become lethargic and may suffer severe swelling of the lymph nodes.
Tuberculosis: Both the human and livestock varieties of TB are likely to increase, particularly the latter as droughts bring livestock and wildlife into closer proximity at watering holes.
Yellow fever: Mosquitoes spread this disease, which causes fever and jaundicelike symptoms, between wildlife and humans, and will likely spread into new areas as the climate changes.