Alzheimer's disease is a more serious disease  Mutations in gene No  4 were once considered a cause of Alzheimer's disease
The probability of Alzheimer's disease in people who are infected with the HSV-1 virus at the same time with the No. 4 mutant gene is two times higher than that of the population with such mutant genes alone.
 However, recently some scientists have proposed that the cause of this complex disease may be simple, that is, some microorganisms that can cause brain infections, such as the HSV-1 virus