virus types
      coronavirus
      arenavirus (arena - have sand)
        lassa
	
      filovirus (have filaments)
      	ebola
	marburg
      flavivurus

etiology - cause of the disease
pathogenesis - biological mechanism that leads to the disease

signs - observed by doctor
symptoms - described by the patient

DNA virus - carries own (usualy double stranded) DNA: smallpox
RNA virus - causes direct protein construction from viral RNA: 
    cold, flu, SARS, COVID-19, West Nile, Ebola, polio, measles
retrovirus - carries RNA, but insde the cell causes to produce DNA then
	    start building viral proteins: HIV

attack rate = number of new cases (per time inteval) in the population at risk/
       	      nmber of people at risk on the population
virulence - ability to infect or damage the host

assay - procedure of measuing the amount or functional activity of
       the target entity (the anlyte)
vector - agent which caries and tranmits the pathogen into another oranism
       
index case (patient zero) - first documented patient in an epidemic,
      may not necessarily be the source
reservoir - a living host of certain species inside which
	  a pathogen survives often (but not always) causing
	  the disease in the reservoir

cox postulate

DISEASES

Smallpox - variola virus 30% death rate
	 variolation - inserting powdered smallpox scabs or fluid to scratches on skin
	 	     1-2% death rate
         vaccination - use (mild) cowpox virus to innoculate
Yellow Fever
Measles
Poliomyelitis - enterovirus (goes through the gut)
Lassa Fever
Ebola
Hantavirus
SARS
West Nile
Mad Cow
the Flu
AIDS