The Navajo reservation is one of the least densely populated parts of the country so that's not it. Lack of infrastructure is a bigger issue. Many if not most o

The Navajo reservation is one of the least densely populated parts of the country so that's not it. Lack of infrastructure is a bigger issue. Many if not most of these people live close to the poverty line and so don't have many options with regard to quarantine. It's not like they can stock up and stay inside for a month. It's also not like the nation can just isolate from the rest of the country. Much of the nation lives and/or works off of the reservation in nearby towns and cities. Bear in mind that by-and-large, the Navajo are not living a traditional subsistence lifestyle anymore. They simply don't have the land or resources to do that so the reservations are not self-sufficient.