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22 May 2024

Virology 101 Series: Types of Viruses and How they Work

by Moderna
Virology 101 Series: Types of Viruses and How they Work

In this series, we’ll explore the basics of virology and demystify the complexities of the science. An important part of understanding virology is knowing that there are different types of viruses. Scientists and researchers have grouped them into categories — like family and genus — based on similar features, like size, shape and the type of genetic material they carry.¹ Let’s take a look at a few types and how they impact the body differently.

Influenza viruses

Influenza epidemics occur seasonally and vary in severity each year, causing respiratory illnesses and placing a substantial burden on healthcare systems. Worldwide, influenza leads to 3-5 million severe cases of influenza and 290,000-650,000 influenza-related respiratory deaths annually, despite the availability of current influenza vaccines. Influenza affects people of all ages, but older adults are disproportionately affected by influenza and its complications.¹

Seasonal influenza spreads easily, with rapid transmission in crowded areas. The most common way it spreads is when an infected person coughs or sneezes, but it can also be spread through hands contaminated with influenza viruses.²


Retroviruses are viruses that leverage RNA as genomic material. When the body is infected with a retrovirus, a cell converts the retroviral RNA into DNA, which in turn is inserted into the DNA of the host cell. The cell then produces more retroviruses, which infect other cells. HIV is an example of a retrovirus.³


Oncoviruses are viruses that can cause cancer. They do this by disrupting regulatory genes in host cells and containing genes that damage cell regulation. Viruses that have been linked to specific cancers include:⁴

  • HPV

  • Epstein-Barr

  • HIV

To learn more about viruses, watch the latest video in our Coffee Break Science series.