Honest about the risks, and specific about what prevents each one.
Malaria
CDC lists transmission areas as all of Rwanda, with chloroquine resistance and P. falciparum as the main parasite. The Government of Canada calls malaria a serious and sometimes fatal disease and recommends antimalarial medication for most travellers here. The tidy, temperate feel of a Rwanda itinerary is not a reason to skip it.
Prevention Prescription tablets, chosen against your route and your other medicines. Plus repellent, long sleeves at dusk and a treated net where the room is open.
Fresh water
The Government of Canada notes a risk of schistosomiasis in Rwanda while saying most travellers are at low risk, and asks travellers to avoid contact with untreated fresh water. CDC describes transmission through wading, swimming, bathing or washing in contaminated fresh water — streams, rivers, ponds, lakes or untreated pools. There is no vaccine and no preventive medication.
Prevention Stay out of it. That includes the tempting bits of Lake Kivu, unless you are in a chlorinated pool. Neither source clears any particular lake, so do not read one into it.
Marburg virus disease
The Government of Canada notes that sporadic outbreaks may occur in Rwanda, and that there is no vaccine or specific treatment, while stating the risk of getting the virus is low if proper precautions are followed.
Prevention Avoid contact with people who are sick and with their blood, body fluids or contaminated objects. Check for current outbreak notices close to departure rather than at booking.
Roads
The Government of Canada describes the road system as generally good and well maintained in Kigali and on main roads, but says most roads outside those areas are unpaved and driving can be dangerous because of insufficient lighting, missing traffic signs, stray livestock and poorly maintained vehicles. Drivers do not always respect traffic laws and sometimes drive at excessive speeds, and roadblocks are common throughout the country.
Prevention Drive defensively, avoid travelling after dark, and use a driver from your operator on the mountain roads. Ask whether your rental includes roadside assistance.
Rabies exposure a long way from a clinic
CDC states rabid dogs are commonly found in Rwanda and rabies is present in some terrestrial wildlife, and adds that if an exposure occurs the vaccines may only be available in larger suburban or urban medical facilities. The gap between where the bite happens and where the treatment is kept is the whole problem.
Prevention Do not touch or feed animals you do not know. Any bite, scratch or lick on broken skin: wash for fifteen minutes with soap and running water, then seek medical advice the same day. Pre-exposure vaccine before you go if your trip puts you far from a city.
Insect-borne illness beyond malaria
CDC names dengue, African tick-bite fever, leptospirosis, hantavirus and tuberculosis among what travellers to Rwanda may encounter. The Government of Canada calls dengue risk sporadic here, with no vaccine or preventive medication available in Canada, and names chikungunya as a risk that varies by season, year, region and elevation.
Prevention Repellent through the day, not just at dusk. Long trousers and closed shoes for trekking and for long grass — tick-bite fever is a walking problem rather than a sleeping one.
Getting treated
Public facilities in Kigali are described by the Government of Canada as adequate for routine procedures, with private facilities better equipped and more expensive, and health care access limited outside the capital. Serious medical problems may require air evacuation to a neighbouring country.
Prevention Travel insurance that names medical evacuation and hospital stays, bought before you go, with the policy number saved offline. Ask your gorilla operator what their own evacuation arrangement is from the trailhead.