Hi ODL and welcome!
First of all, know that you are not alone in this fear. There are many of us here with varying degrees of emetophobia.
You have taken good precautions against getting the virus from your brother...so now all you can do is trust that you will stay well.
Part of getting past this fear is accepting that there is only so much control that we have over circumstances, such as getting sick.
Here is a link to our Resources. In it you will find two books specifically on health anxiety. One of them includes a chapter on fear of vomiting. It could be helpful to you.
https://www.healingwell.com/community/default.aspx?f=9&m=104206
Otherwise, know that you have done all that you can to stay healthy, and try keep your focus positive.:)
Scaredy Cat