Travel insurance for Tahoua comes with a complication that matters more than anything else on this page: Tahoua sits within Niger, and many governments currently advise against all travel, or all but essential travel, to this part of the country, which changes what any policy can honestly promise. Before anything else, check your own government's current advisory for Niger and this specific region, since that status is what most insurers look at first when a claim is filed.
The practical effect is significant. Many travel insurance policies contain a standard exclusion for trips to, or within, a country or region under a do-not-travel advisory, meaning claims arising during that trip - medical, cancellation, lost belongings, anything - can be declined regardless of what actually happens on the ground. This is common wording across the industry rather than a quirk of any single provider, and it applies whether the advisory covers the capital, Niamey, or a regional center like Tahoua specifically.
Access itself reflects the same reality. International commercial service into Niger has been limited for some years, and onward travel to Tahoua from Niamey depends on domestic transport whose availability can change with little notice; do not assume any particular route or schedule without checking current conditions directly before booking anything.
If you are set on travel here for essential or professional reasons, the honest step is to contact insurers directly, disclose Niger and Tahoua specifically as the destination, and get any advisory-related exclusion confirmed in writing rather than assumed from general terms. Do not assume a standard policy covers travel a government currently advises against; check the wording explicitly, and check whether your existing health cover extends abroad and to this region at all before relying on it for anything beyond routine planning that never actually leaves the ground.