It can be a real challenge to keep students interested in the course content, but I think one way that instructors can continually do so is to ask students on a weekly basis if they have questions or concerns on anything from previous/current/upcoming weeks, because usually this will get some kind of response from them, whether straight to the point or a lengthy answer. In almost every case where I have asked this at the beginning of a live chat, I have had at least 5-10 students provide an answer. Also, I ask the students what they think will be most interesting for them to research/learn about for a particular week, because I think in this way they feel like there's a space to share their interests and thoughts and to hear my feedback right away. I think by keeping students participating, in my opinion, that is the best way to keep them interested and engaged in the classroom from week to week, especially in an online environment.