An infectious disease is caused by germs such as bacteria and viruses. Lyme disease, for example, is spread to people through an infected tick’s bite. When the disease spreads directly from one person to another, it is said to be contagious. Contagious diseases such as colds or the flu are spread by direct physical contact, sneezes, coughs or touching something an infected person has used. Some common contagious diseases can be prevented by vaccinations.
Usual Childhood Diseases
Contagious diseases such as measles, mumps and chickenpox were once called the “usual childhood diseases” because children and teens caught them as they were growing up. With the advent of vaccinations, these diseases occur less frequently, although they still occur in teens who have not been vaccinated and sometimes even in teens who have been vaccinated. A few very contagious and very dangerous diseases, such as diphtheria and polio, are rarely seen today. Other contagious diseases, such as most sexually transmitted diseases and infectious mononucleosis, cannot be prevented with vaccination.
“Respiratory spread” means a disease that is spread by infected droplets in a person’s saliva, breath, sneeze or cough. Most of the contagious diseases that affect teenagers are more likely to be spread by this method. Measles, for example, is so contagious that a teen can contract the disease just by walking into a room from which an infected person has already left, according to the Centers for Disease Control and Prevention (CDC). German measles, diphtheria, influenza, chicken pox, mumps, meningococcal disease and pertussis -- also called whooping cough -- are all spread through infected droplets. Some, such as mumps, can also be spread when a teen handles something that an infected person has touched recently.
Blood and Body Fluids
Hepatitis A is spread through contact with an infected person’s feces or -- if she fails to wash her hands after using the toilet -- through something she has touched. Hepatitis B is spread through direct contact with an infected person’s blood or body fluids. Polio can be spread in the same way as hepatitis A as well as through infected respiratory droplets. Sexually transmitted diseases, as the name implies, usually result from direct sexual contact, but can also result from skin-to-skin contact with an infected sore. Human papillomavirus, or HPV, is a virus that causes genital warts rather than an actual disease and is also spread through sexual contact with an infected person.
Some contagious diseases in teens can have lifelong effects. Polio, although rarely seen today, can cause severe paralysis. Chicken pox can result in scarring from the blisters and cause birth defects if the teen who contracts it is in the first three months of pregnancy. German measles is another contagious disease that can affect the unborn child of a pregnant teen and cause mental retardation, visual and hearing problems, according to the CDC. Regular measles can cause encephalitis, a serious inflammation of the brain, according to the Vermont Department of Health. Mumps can make male teens permanently sterile.
Vaccination can prevent or lessen the severity of most contagious diseases in teens. Pertussis vaccine, for example, is not 100 percent effective, according to the CDC, and a vaccinated teen can still catch the disease. Vaccinations are not available for the common cold or sexually transmitted diseases. Frequent hand washing is the best way to prevent the first and abstinence or consistent use of a condom can help prevent the second. Avoiding people who are known to be ill is also helpful in preventing the spread of contagious diseases such as measles, mumps and chicken pox.