Yes, and no. If the Zombification Virus was genetically modified, and released in a large enough quantity it might be possible. The water supply poisoning scenario is nearly extremely low due to the dilution of the water itself. However if the virus was sprayed from a plane right above you then your odds of contracting the nefarious necrosis would be much greater. Luckily the odds are still slim since the only 100% known method of transmission is through being bitten by a living dead rotted corpse hell bent on ingesting your brains, and other vital organs. Their saliva is the main carrier of this living deadly virus. There’s also a minimal chance of acquiring the zombie virus through blood splatters flying about your face when eradicating the dead rising from their unholy graves. If you come face to face with a zombie then please run away, and call your nearest zombie slaying firm. Never take on a re-animated corpse on your own! It’s just not worth the risk to your life!