Infection is the invasion by and multiplication of 'foreign' microorganisms that can cause pathological conditions or diseases in the host organism. Uropathogenic Escherichia coli infection of a ...

Viral infection is the invasion of the body by a small agent known as a virus. Viruses replicate inside host cells and can produce toxins that cause disease. The immune system helps to destroy viruses ...

Your son is almost certainly going into puberty, which would explain why he is starting to grow now. Both boys and girls show changes in their breasts at puberty. The areola or area around the nipple ...