I am writing a novel and am trying to come up with a theoretically sound way for mankind be overrun with sometime of viral, bacterial, fungal, etc. evolution which our bodies would be completely incapable of battling without a Homo Sapiens evolution as well. This condition, attack on our species, needs to specifically attack the brain and be able to cause a variety of conditions such as Alzheimer’s, Cerebral Palsy, Multiple Sclerosis, Parkinson’s, Huntington’s, Pick’s disease, ALS, Dementia, etc. Any creative and knowledgeable input would be greatly appreciated. Thank you.

http://en.wikipedia.org/wiki/Ophiocordyceps_unilateralisyou could make something much more sinister than this

http://en.wikipedia....ps_unilateralisyou could make something much more sinister than this

 

The real life zombie virus that affects ants yeah that's cool

The computer game The Last of Us is very loosely based on a form of cordyceps that parasitises human hosts

Naegleria fowleri /nəˈɡlɪəriə/ (also known as the "brain-eating amoeba") is a free-living, thermophilic excavate form of protist typically found in warm bodies of fresh water, such as ponds, lakes, rivers, and hot springs. It is also found in soil, near warm-water discharges of industrial plants, and in poorly chlorinated, or unchlorinated swimming pools, in an amoeboid or temporary flagellate stage. There is no evidence of this organism living in salt water. It is an amoeba belonging to the phylum Percolozoa. N. fowleri can invade and attack the human nervous system and brain, causing primary amoebic meningoencephalitis (PAM). Although this occurs rarely,[1] such an infection nearly always results in the death of the victim.[2] The case fatality rate is greater than 95%.

 

http://en.wikipedia.org/wiki/Naegleria_fowleri

Transmissible spongiform encephalopathies

http://en.wikipedia.org/wiki/Transmissible_spongiform_encephalopathy

 

here, a protien is transmitted usually through consumption of infected food but also shows up on occasion as an inherited trait..

 

"Familial forms of prion disease are caused by inherited mutations in the PRNP gene. Only a small percentage of all cases of prion disease run in families, however. Most cases of prion disease are sporadic, which means they occur in people without any known risk factors or gene mutations. In rare circumstances, prion diseases also can be transmitted by exposure to prion-contaminated tissues or other biological materials obtained from individuals with prion disease."

 

night of the living dead....

rabies.

Rabies Virus ( of the genus lyssavirus) is a negative sense single stranded rna virus and is one of the viral causes of rabies in humans. Has a short incubation period of about 4 days and can take as long as 12 weeks for the first symptoms. Aside from flu like symptoms, aggression, confusion and partial paralysis can also occur.

 

"Death almost always occurs 2 to 10 days after first symptoms."

 

http://en.wikipedia.org/wiki/Rabies#Cause

http://www.ncbi.nlm.nih.gov/books/NBK8618/

http://en.wikipedia.org/wiki/Rabies_virus#Life_cycle