Gravitational interaction between the Moon and Earth orbiting each other and the Sun …
Moon/Earth were formed within the influence of the Sun and the solar system.
Unless a giant comet ( attracted by Sun’s larger gravity well?? ) introduced something extra-solar , almost everything is under the influence of the Sun.
Almost all illnesses are worth avoiding. Take for example, malaria. Dengue has 4-variants which can kill if you’ve already got any one of others the first time. COVID still hasnt been fully researched yet.