It is strange. Is there more published information about the tourist guide? Perhaps it's a very rare case because she had other health problems.

Perhaps 99% of the people get enough immunity. Vaccines don't have a 100% of immunity protection neither.

The video linked in the article doesn't add much more information. Note that the written description says

> So, they need to prevent infection by increasing their physical activity, says Chinese expert.

that doesn't make any sense, but the translation in the video says

> cured patients should enhance their own health safeguards

Edit: I found https://globalnews.ca/news/6623287/coronavirus-multiple-infe... and https://www.reuters.com/article/us-china-health-japan/japane... . It's not very clear, but it looks like a continuation of the first infection after a few week of no symptoms. Anyway, another reason not to infect 50% of the population on purpose.