Science Buddies: "Ask an Expert"

why is it that the influenza virus only infect humans, mammals, and birds but not reptiles, fish, or insects?

Hi,

That's a great question. I had trouble finding information on that from web searches. Generally: The immune system of those other animals doesn't recognize the virus and so it doesn't react. But the virus could get in - and is likely not being replicated (very efficiently) - so perhaps something is different about the cell's machinery for replication - it doesn't work with mammalian virus. I KNOW there are reptilian viruses, and also insect viruses that do not affect humans, so it seems to work both ways.

If any other experts have more insight - I would love to hear it. What an interesting question!

Tonya

Hi there,

You have a very interesting question, and Tonya has already offered some great insight.

Another thing to consider is that viruses usually "find" their host cells by interacting with surface proteins on the cell membrane (in animals) or cell wall (in other organisms). Different types of animals express different cell surface proteins, so it's possible that influenza recognizes cell surface proteins in mammals and birds that are not expressed in other animals.

Another important thing to consider is that mammals and birds are endotherms ("warm-blooded"), which means they have a relatively constant, warm core body temperature. This may be important for the flu virus. Reptiles, fish, and insects are all ectotherms ("cold-blooded"), which means their body temperature depends on the environment and can sometimes fluctuate a lot more.

I hope this gets you thinking. Please post again (in this same thread) if you have more questions. I'm interested to find out where this project goes!

Heather