An online asynchronous course offers many benefits and opportunities, but it does not come without certain challenges.   Nothing can replace the human connection that a student needs to succeed in a course.  In the first two weeks of class, you should place a focus on establishing presence, clarity, and human connection.  You are probably used to creating a welcome post in the announcements, but this semester you may want to try and take it up a notch by creating a short welcome video instead. In the video you could introduce yourself, explain the purpose of the course, and communicate enthusiasm for the subject.  (Just like you would in a face-to-face course!)  You may also want to pair this with an additional video that steps the students through the navigation of the course. 

Another area you can improve upon early engagement is within the first week assignments.   Do not forego the introductory discussion board, and make sure you are frequently posting and responding to each student in a substantive manner.  But after that, make sure you also provide an activity that will challenge the students intellectually, but at the same lay the cornerstone to their confidence in the course.  Consider using a short video or simulation and pair it with guided questions that prompt curiosity rather than assessment pressure.  Early formative assignments such as simple data interpretations or reflections prompts help students practice scientific thinking while learning how feedback works in your course.  Just like the introductory discussion board, make sure your feedback is prompt and substantive.