Pretty easy when you know how...
Bacteria
Normal game
Casual difficulty
Gene setup:
ATP Boost
Aquacyte
Trans-Stasis
Creationist or Genetic Mimic
Extremophile
Start in India and evolve the following transmissions in order:
Water I
Air I
Water II
Air II
Extreme Bioaerosol
Livestock I
Livestock II
If any symptoms appear at any point de-evolve them
Now unlock these abilities in order:
Cold Resistance I
Drug Resistance I
Cold Resistance II
Drug Resistance II
Genetic Hardening I
Genetic Hardening II
The final step is to unlock these symptoms:
Coughing
Pneumonia
Nausea
Vomiting
Diarrhoea
Insomnia
Sneezing
Once you grab sneezing the achievement should pop.