Alzheimer's disease: Questions Raised by a Herpes Virus Origin

As in the case of other CNS infectious agents claimed to cause Alzheimer’s disease [AD], the theory that Herpes Simplex Virus or any other herpes virus causes AD is still controversial. In their 2013 review, Mawanda and Wallace’s Can Infections Cause Alzheimer’s Disease ¹ gave seven annotated references as to why HSV-1 “remains questionable” as a cause for Alzheimer’s. Some say that Herpes simplex virus type 1 in conjunction with APOE-epsilon 4 allele is a strong risk factor for AD, though either of these features alone do not increase the risk for AD. It is claimed that people who have symptoms of late onset Alzheimer’s disease (AD) and have one or more APOE-ε4 gene copies are more likely to have AD. However, APOE- ε 4 is not diagnostic of AD and should not be used to screen people or their family members. Furthermore, many of those who have e4 alleles will never develop AD. And even in symptomatic people, only about 60% of those with late onset AD will have APOE- ε 4 alleles.^2,3 Not only is the APOE gene not a clinical diagnosis, but just as importantly, “negative” results do not confer later protection. Beyond APOE, there are at least 20 other genetic factors which have been shown to have a small but significant role in determining Alzheimer risk.⁴ And true understanding of genetic test results also requires attention to potential inaccurate results. For example, APOE- ε 4 alleles themselves are known to show a distinct increase in tuberculosis.⁵ Before widespread institution of anti-herpetics is unleashed on the general population, this is an area which requires further research.