Polio is a contagious viral illness that in its most severe form causes paralysis, difficulty breathing and sometimes death.
The poliovirus resides only in humans and enters the environment in the feces of someone who’s infected. Poliovirus spreads primarily through the fecal-oral route, especially in areas where sanitation is inadequate. Poliovirus can be transmitted through contaminated water and food or through direct contact with someone infected with the virus. Polio is so contagious that anyone living with a recently infected person is likely to become infected too. Although people carrying the poliovirus are most contagious seven to 10 days before and after signs and symptoms appear, they can spread the virus for weeks in their feces.
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Hepatitis A virus is one of six currently identified strains of viral hepatitis — the others are B, C, D, E and G. The strains differ in severity and in the way they spread. Hepatitis A is a highly contagious liver infection caused by the hepatitis A virus. Although not usually as serious as other types of viral hepatitis, hepatitis A causes inflammation that affects your liver’s ability to function.
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Hepatitis C is a virus that often silently attacks your liver. Hepatitis C is one of six identified hepatitis viruses — the others are A, B, D, E and G. All cause the liver to become inflamed, which interferes with its ability to function. Hepatitis C is generally considered to be among the most serious of these viruses. Most people infected with the hepatitis C virus (HCV) have no symptoms at all. In fact, most people don’t know they have the disease until liver damage shows up, decades later, during routine medical tests. Although vaccines exist for hepatitis A and B, no vaccine for hepatitis C has been developed.
Over time, if you have a hepatitis C infection, it can lead to liver cancer, liver failure or cirrhosis — irreversible and potentially fatal scarring of the liver. Unlike HIV, the virus that causes AIDS, the hepatitis C virus usually isn’t transmitted through sexual contact. Instead, you’re more at risk if you’re exposed to contaminated blood — through needles shared during drug use or through blood transfusions.
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Genital herpes is a highly contagious sexually transmitted disease. Genital herpes is common, affecting both men and women. Features of genital herpes include pain, itching and sores in your genital area. The cause of genital herpes is a strain of herpes simplex virus (HSV), which enters your body through small breaks in your skin or mucous membranes. Sexual contact is the primary way that the virus spreads. There’s no cure for this recurrent infection, which may cause embarrassment and emotional distress.
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Viral hemorrhagic fevers (VHFs) are caused by viruses from four distinct families and range in severity from relatively mild to life-threatening. When they do occur, they’re often found in people who’ve recently traveled internationally. Although all begin with fever and muscle aches, some viral hemorrhagic fevers progress to more serious problems, including severe internal and external bleeding (hemorrhage), widespread tissue death (necrosis), and shock. No current treatment can cure viral hemorrhagic fevers. Immunizations exist for only two of the many viral hemorrhagic fevers. Until additional vaccines are developed, the best approach is prevention.
The VHF designation includes a broad range of diseases. Signs and symptoms can vary widely, even among members of the same viral family. But VHFs do have some common characteristics, especially in their effects on your vascular system — the network of arteries, veins and capillaries that circulates blood throughout your body.
Hemorrhagic fevers make blood vessels more permeable — that is, more likely to leak — causing bleeding that can range from relatively minor to massive. Bleeding may occur under your skin, in internal organs, and from your mouth, eyes, ears and rectum. People with severe bleeding may experience potentially lethal signs and symptoms such as shock and coma, but rarely die of blood loss.
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