| virus(noun, illness, bug, death, toxin) |
| microbe(noun, illness, sickness, bug, beings) |
| bug(noun, informal, illness, sickness, beings) |
| origin(noun, cause, beginning, source, basis) |
| seed(noun, cause, start, influence, base) |
| bud(noun, cause, start, plant, beginning) |
| egg(noun, cause, influence, connection, beginning) |
| nucleus(noun, quality, cause, start, character) |
| source(noun, cause, start, base, beginning) |
| bacteria(noun, microorganism, micro-organism) |
| embryo(noun, cause, start, influence, base) |
| root(noun, quality, cause, character, spirit) |
| bacterium(noun, illness, unit, sickness, bug) |
| bacillus(noun, illness, sickness, microorganism, bacteria) |
| beginning(noun, cause, start, base, stone) |
| microorganism(noun, illness, unit, sickness, bug) |
| rudiment(noun, cause, beginning, stone, source) |
| cause(noun, plan, influence, beginning, source) |
| inception(noun, cause, influence, beginning, source) |
| start(noun, cause, base, beginning, stone) |