Are there any methods other than cleaning and airing?

Well, there are probably some lamps, like in hospitals. But I don't know if you can use them at home and what kind of lights are needed. Maybe you should buy an air filter, I saw on the Internet. But I don't know how effective they are against germs.

Now there are special air purifiers, but you need to know how and where to apply them correctly. This is quite a complex subject, it is not necessary to understand. You can start by reading the information and check this site, there are many useful articles on this topic. At the same time and be able to read about cleaners and their applications. I think you'll find it useful.