HIV vs. Pneumonia Bacteria: Size Comparison & Causes

Pneumonia is not caused by a bacteria, but by a fungi, virus or bacteria. In most cases pneumonia is caused by the bacteria such as Streptococcus pneumoniae or Staphylococcus aureus.

The Human Immunodeficiency Virus (HIV) is much smaller than the pneumonia bacteria. HIV is a retrovirus, meaning it carries its genetic information in RNA form instead of DNA. The size of HIV is approximately 100 to 120 nanometers (nm), while the size of pneumonia varies depending on the type of bacteria causing the infection. For example, Streptococcus pneumoniae, a common cause of pneumonia, is about 1 to 2 micrometers (µm) in size. Therefore, the pneumonia bacteria is about 10 to 20 times larger than the HIV virus.