When immunity is low, germs throw a party

When a person's CD4 levels go down below 500 they start getting opportunistic infections. [iStockphoto]

Like their name suggests, opportunistic infections 'take the opportunity' when they have the chance. In more medical terms, they are infections that attack a person at a time when their body's immunity is below normal.

"We encounter germs on a daily basis. In fact, we have billions of microorganisms that live in and on us.