RNA virus Facts for Kids

RNA viruses are tiny living things called viruses that use a special molecule called RNA as their main instruction book, like a blueprint. This is different from many other living things, including us, which use DNA.

Some well-known diseases in humans caused by RNA viruses include SARS, the flu, and Hepatitis C. Viruses that use DNA instead of RNA are called DNA viruses.

Scientists have ways to group and classify viruses. One important system was created by David Baltimore, who won a Nobel Prize. In his system, RNA viruses are put into different groups based on how their RNA works:

Group IV: These are called (+)ssRNA viruses. The "sense" RNA in these viruses is like a ready-to-use message that cells can read to make proteins. Examples include Picornaviruses and Togaviruses.
Group V: These are called (−)ssRNA viruses. Their RNA is "antisense," meaning it's the opposite of the message needed to make proteins. It needs to be copied first. Examples are Orthomyxoviruses and Rhabdoviruses.
Group VI: These are ssRNA-RT viruses. They have "sense" RNA, but they also use a DNA step in their life cycle. A good example is Retroviruses.

Another way viruses are classified is by the International Committee on Taxonomy of Viruses (ICTV). This system uses terms similar to how animals and plants are grouped, like orders and families.

Why do RNA viruses change so much?
Related pages
Images for kids
See also

Why do RNA viruses change so much?

RNA viruses change, or mutate, much faster than DNA viruses. This happens because the special tools they use to copy their RNA, called viral RNA polymerases, are not very good at checking for mistakes. They don't have a "proof-reading" ability like the tools that copy DNA.

This high mutation rate is why it's often hard to make good vaccines to protect against diseases caused by RNA viruses. The virus keeps changing its appearance, making it difficult for vaccines to target it effectively.

Some parts of an RNA virus's instruction book are super important and can't change much. For example, a part of the hepatitis C virus's instruction book that helps it start making proteins is very similar in all hepatitis C viruses. This is because it's essential for the virus to work and make copies of itself.