By common consent the term "infectious" is restricted to those diseases caused by the invasion and multiplication of certain very minute unicellular organisms included under the general classes of bacteria and protozoa.
"Special Report on Diseases of Cattle"
U.S. Department of Agriculture J.R. Mohler
Drupe oblong, compressed, unicellular.
"The Medicinal Plants of the Philippines"
T. H. Pardo de Tavera
Yes, and as such may be classed the drops of life known as unicellular organisms.
"The Kempton-Wace Letters"
Jack London Anna Strunsky