If you’re self isolating due to flu-like symptoms, you should not leave the house at all.
If you're sick with COVID-19 the RSPCA currently recommends: "restricting contact with your pets and other animals just like you would around other people. You also need to avoid petting, snuggling, being kissed or licked and sharing food. This is not because there have been reports of pets or other animals becoming sick with the virus but we still don't know everything about the virus."
Here’s further advice regarding self isolation.