Overview
Phyrexian Infection (Golgariosa Phyresis) is a highly virulent disease... I mean deck. It's a modern deck.
Signs and Symptoms
Infection with Golgariosa Phyresis can be diagnosed when opponent receives one or more poison counters . As soon as that happens the onset of disease is rapid and will likely lead to death, I mean victory, by round 3 and with good opening hand by round 2. We don't worry about life total here, as soon as that 10th poison counter hits - opponent is done for.
Vectors of Infection
Common carriers of the disease are Mirrodin natives Glistener Elf and Ichorclaw Myr as well as highly dangerous insect called Plague Stinger. One should also avoid contact with Inkmoth Nexus which can also deliver the infection. Finally, in the recent years an emergence of Venerated Rotpriest has caused a spike in virulence and deaths caused by Phyrexian Infection.
Virulence Factors
High lethality of Golgariosa Phyresis can be attributed to Groundswell, Might of Old Krosa, Mutagenic Growth and kicked Vines of Vastwood. In the right conditions a single 1/1 Glistener Elf can deliver a stunning 10 poison counters unless blocked, but a lower number is more likely. The elimination of carriers such as aforementioned Glistener Elf and the deadly Plague Stinger can prove near impossible due to Blossoming Defense, Veil of Summer and Vines of Vastwood. The presence of the Venerated Rotpriest causes a spike in virulence as any use of the above will yield additional poison counters.
Environment
First off - there are 19 lands here not 15! (see: Inkmoth Nexus which is also another vector of infection).
The warm and putrid climate of Llanowar Wastes and Overgrown Tomb found in the deep Forest are ideal for the hosts of this infection and allow it rapid onset. Even without aforementioned instant virulence factors, places such as Cathedral of War and Pendelhaven can easily change a mere 1/1 infection host into a hulking 3/3 that causes a serious threat to the infected.
Prevention
There is no known cure for Phyrexian Infection. Unless the infected can fight off the disease before the 10th poison counter - there is little that can be done. Abrupt Decay will likely follow and Dismember is not uncommon.
as the former didn't work well with just 5 Forest