Because the immune systems of children are not fully developed, and because children are often in close proximity to one another in environments such as day-care centers, classrooms, and on school buses, the transmission of contagious diseases is particularly easy.
Contagious diseases are often caused by the spread of bacteria (such as in scarlet fever) or viruses (such as in chickenpox, measles, hand-foot-and-mouth disease, and several others) in droplets of saliva and mucus, especially when coughing or sneezing. Contagious diseases can also occur by coming in close personal contact with another infected person or even by sharing personal items, as in infestation caused by insects (such as with scabies) or a fungal infection (such as in ringworm).
Many childhood diseases, once contracted, result in lifelong immunity, but this is not always the case. Vaccinations also provide immunity to some of the diseases below. Unfortunately, many of these diseases are most contagious before the infected child has any symptoms of the disease, making transmission even more likely.
Fifth disease, also called slapped-cheek disease, is a common illness in young children caused by a parvovirus. Fifth disease is spread by contact with others who are infected, specifically by exposure to fluid from the nose. The illness lasts approximately five days, but the rash can keep coming back for a few weeks, particularly with exercise, heat, fever, or stress. If a pregnant woman becomes infected, the infection can be harmful to the unborn baby. Fifth disease can also cause arthritis, although this is more commonly seen in infected adults.
Roseola, also known as sixth disease, is a mild illness, mainly affecting children, which will go away on its own
Measles (rubeola) is a highly contagious infection of the respiratory system, which is caused by a virus. The incubation period is usually asymptomatic and lasts from 10-14 days. This is followed by a prodromal period of two to three days, which is accompanied by redness of the eyes, nasal discharge, and cough. An eruption inside the mouth, called Koplik's spots, may occur, is only found in measles, and may precede the rash by a couple days. The characteristic rash starts on the face, then moves down the neck to the trunk and finally the extremities. The patient typically starts to improve within 48 hours of the appearance of the rash, although cough may persist for one to two weeks thereafter.
Chickenpox (varicella) is an extremely contagious childhood disease caused by the varicella-zoster virus. Winter and spring are the most common times of the year for chickenpox to occur.
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