New, persistent leg pain certainly warrants a visit to your doctor for evaluation. Leg pain can have many causes, but your description of aching after prolonged standing or sitting suggests a possible buildup of fluid in the leg veins (chronic venous disease, venous insufficiency).

As you might think, bacterial infections are caused by bacteria, and viral infections are caused by viruses. Perhaps the most important distinction between bacteria and viruses is that antibiotic drugs usually kill bacteria, but they aren't effective against viruses.

Certain types of osteoporosis drugs have been associated with an increased risk of two rare but serious problems - osteonecrosis of the jaw and an unusual type of fracture in the upper thigh bone (femur).

Early HIV symptoms usually occur within a couple of weeks to a month or two after infection and are often like a bad case of the flu. In many people, early HIV signs and symptoms include:

Children need vaccines early because they are susceptible to disease at a young age. Infectious diseases can be life-threatening for infants and young children.