It is an unfortunate and an unpredictable situation if it arises and is a likely incident at times if you are traveling in a group. However it doesn’t mean that it will jeopardize your entire trip.  The one who gets sick is attended with proper care whereas the rest team members will go on with the trek ahead.  The sick person will be taken care of, the rest of the group will be able to continue with the trip. Also the team leader will assess the condition and is the authorized person to make a rationale decision. The leader is the best person to decide whether to trek further or return to a lower elevation and wait for the rest of the group.  If the condition is extremely serious then the person will be flown by air ambulance to Kathmandu or Pokhara for expert medical attention. The rest of the group will go on with the trek as per the itinerary.