What are four examples of fluids by which viruses can spread?

In humans, viruses can spread in many ways. Four fluids
that can be used by viruses to spread are:

• Air:
  examples of viruses that spread through air are those that cause influenza and the
  common cold. When people with these illnesses sneeze or cough the viruses are spread to
  others.

• Water: viruses that cause
  illnesses like gastroenteritis are spread from one person to another by infected water.
  

• Blood: a large number of viruses
  are spread through blood. Diseases like West Nile Fever can be spread through vectors
  that suck blood. As the viruses can survive in the vector's body also they are spread
  when the same animal bites a person who is sick and then bites a healthy person. Some
  viruses like HIV cannot survive in a vector's body. They are spread when a healthy
  person's blood comes in contact with blood from someone who is sick through infected
  needles, or during blood
  transfusions.

• Sexual fluids: viruses
  which include HIV are spread though sexual fluids like semen and vaginal fluids. This
  usually happens during sexual
  intercourse.