The main issue is attempting to do anything that isn't the zombie infestation gets challenging to do, mainly since participant zombies like to hangout at quest givers and other areas where lots of classic gold wow players have a tendency to collect. Because this event also will come with a whole questline that occurs in the zones around Stormwind and Orgrimmar, there is ample opportunity to camp outside and possibly infect as many players as possible. However, one positive shift from the previous time the zombie infestation happened is that Blizzard seems to have made it more challenging to disperse it into the rest of Azeroth. Among the first things I did once I got infected was to hearth to Dalaran, but when I came, I was not infected anymore. However, I managed to carry it to Boralus through utilizing the portal site in the mage tower, so it is not a perfect program yet.
The major point to realize is two distinct events are going on. There's the scourge invasion as well as the questline, which requires players to Icecrown and sends gamers on a goose hunt for Nathanos. Then there's the zombie infestation, which adds a small PvP aspect to everything. It is not surprising a few people would want to get involved in the very first event but not the moment, as not everyone likes PvP or using their class and race skills removed and replaced by other abilities. Blizzard could make the infestation only active for one of the months of the invasion, however, that's no fun for anybody who misses that week and might want to participate. Honestly, the best solution likely is to leverage the Warmode system. An infestation is essentially a PvP event anyways, so having the capability to opt-in with Warmode makes sense. Even doing something where for the majority of the invasion, players had to opt into the infestation by selecting Warmode, but then at the last week, until Shadowlands fell, the infestation could influence everyone, would probably be the best solution.
Last week Blizzard announced they are having gamers vote for another mount, wNg to be the toughest World of Warcraft expansion nonetheless, with fresh Ray Tracing features currently in the beta, a new graphics recommendation of GTX 1080 or RX Vega 64, and presently a 100GB SSD requirement. I'm sure lots of cheap wow classic gold diehards will be upgrading their PCs to run this new expansion.