The infection spreads through your upper respiratory tract and sometimes goes right into your lungs. The virus typically sweeps through large groups of people who share space, such as schools, working environments and nursing homes. Although both colds and influenza stem from viruses that infect the upper respiratory tract, the symptoms of influenza are more pronounced and its complications more severe. A runway case of influenza can develop into a more serious illness, such as pneumonia. The infamous Spanish Flu of 1918 killed 20 million people worldwide.
Experts say another pandemic is inevitable, which no vaccine can prevent.
Both the cold and flu are caused by viruses, which are infectious micro-organisms that invade your body and can make you sick. You catch these bugs by inhaling water droplets in the air from the breath of an infected person, who spews them out every time he or she exhales, coughs, or sneezes. Cold and flu viruses can roost on inanimate objects too. Turn a contaminated doorknob or use a co-workers pencil before touching your lips, and you can become infected. So wash your hands with warm soapy water and use a paper towel or your elbow to shut the water off to avoid recontamination.