Hong Kong Public Libraries & bed mites
A note even though all libraries are closed at the moment. There may be bed mites in the spines of the books. That includes ALL books in local public libraries as they are being circulated around the city. Once those bugs got into your home, you may not recognize it immediately. You may not notice it untils months later until they are grown.
Annoyance may start as they do not bite everyone. But if you find just a handle of them, you'd better start checking all tight spaces and under the bed mattress and around the bed frame and spray them with things like dustmitetex solution by following a schedule for a period of time. Some may even use industrial hot air guns to kill the eggs embedded in the mattress or frame or anything else. Just be careful not to burn down the bed or the flat.