Cold and Flu
Conditions and Diseases
Swine Flu (H1N1/09)
Ebola Hemorrhagic Fever
Cell Biology (cytology)
HIV and AIDS
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses display a wide diversity of shapes and sizes, called morphologies. Generally viruses are much smaller than bacteria. Most viruses that have been studied have a diameter between 10 and 300 nanometres.
Why is the flu common in the winter, but less common in the summer?
In climates that experience winter, the influenza virus tends to survive longer and transmit itself better in cold and dry conditions, which leads to more people contracting the flu during those colder months. In climates that do not have a winter season, however, the flu is more common in periods of high humidity and lots of rain. Scientists aren’t sure why that is, but it doesn’t seem to have to do with the immune system...