Syphilis
This disease has not been chosen № 1 by chance in our list. In the middle ages it mowed down whole cities and nations. You can get this infection just drinking from a glass which has been used by an infected person. But, do not worry since in general statistics such cases make up insignificant percent. Syphilis is mainly transmitted during sexual intercourse.
Approximately one month after the infection gets into body, a syphilitic ulcer is formed in the spot where the ingress of microbes occurred. It represents a dense red area of the skin about 1 centimeter in diameter. However, in this stage the laboratory tests are unable to detect the infectious agent in blood. Elevated temperature and worsening of general health condition are also characteristic for this stage.
Only in 6-8 weeks the test will show the presence of the syphilitic agent. In this stage the mucous membranes of syphilitic patients break into rashes. Other associated diseases may be instigated. Syphilitic alopecia and visual impairment are also common symptoms in this stage.
If not cured the disease affects all internal organs and skeleton in a few years. The organs and tissues start to deform and finally the disease may lead to lethal outcome if not treated.