Stepson doesn't shower

Please offer some advice..we get him every other weekend, he's 14 and he brags about how he hasn't showered in days when he gets here. Its disgusting and we just had a baby in November so I'm worried he's going to get her sick because he doesn't practice basic hygiene methods. I usually make him shower on Friday when we get him but I don't think one shower a week is enough to ward off germs. My SO talks to him about this too but its a never ending battle with my stepson. There's no use in talking to his Mom since my husband said she does the same thing. Please offer some advice.