In the fanfiction, it might be that there was a special event. For example, a big gathering where people from different places came together. One of the guests had the flu but didn't know it. Demelza interacted with this person, like sharing a drink or just being in close proximity for a long time, and as a result, she got the flu.
It could lead to her being bedridden for a while. And this might make other characters worry about her. For example, Poldark himself would be very concerned and might neglect some of his own affairs to take care of her.
It could also be that she came into contact with someone who was ill. In the close - knit community in Poldark, diseases can spread easily. If she was near a person with an infectious illness, she might have caught it and developed a fever as a result.
Ross would be extremely worried. He would likely call for the doctor right away and stay by Demelza's side, constantly checking on her temperature and making sure she was comfortable.
A common theme is the exploration of their deep emotional connection. Fanfictions often dig deeper into how they understand each other on a very profound level.
One great piece of Ross Poldark and Demelza love fanfiction is 'The Unspoken Promises' on FanFiction.net. It beautifully delves into their relationship, exploring the unsaid emotions between them in a very tender way.
Well, it could be about Shinichi being really sick with the flu. Maybe he tries to solve a mystery even while he's ill, but his body is weak and his mind is a bit foggy, so he has to rely more on his friends. His friends could be worried about him and try to take care of him while also helping him with the case.
Shinichi is a given as the main character with the flu. But his detective friends, like Heiji, could be important characters too. Heiji might come to visit Shinichi and end up getting involved in a mini - mystery that is somehow related to Shinichi's flu situation, like someone trying to steal a medicine that could cure Shinichi.
Novel flu is basically a flu strain that's emerged recently and isn't familiar to our immune systems. Common flu, on the other hand, our bodies might have some defense against. Novel flu can spread more easily and have more unpredictable effects on health.