While it is just recently found out, QPX, a parasite for clams, has shown a lot about itself. QPX stands for Quahog Parasite Unknown. It infects a certain subspecies of hard clams (Mercenaria mercenaria) called Quahog clams. QPX is a single-celled microscopic parasite that fortunately is a species-specific parasite. This means the parasite specifically affect northern hard clams, or Quahog clams. However, cases of abalone, sea hares, squid, and octopus infected with QPX have arisen. It is scientifically debated on what type of parasite QPX is. QPX, in one theory, are facultative parasites which mean that they are able to live on their own without a host. The other theory is that QPX is an obligate parasite, a parasite that must live with its host during one mandatory section of the life cycle. Both theories are hypotheses and it is still unknown on how QPX infects its hosts. Reports of QPX originated in New Brunswick, Canada in 1959 and in Barnegat Bay, New Jersey in 1976. However, it was finally noticed in the 1990s when mass die-offs of clams were occurring in the Northeast and Mid-Atlantic. Signs of QPX in Quahog clams are decreased new shell growth, swollen and discolored mantles, chipping shell edges, and death. The QPX parasite was found most frequently in the mantle and gills of clams. Quahog clams usually show an intense inflammatory response to the parasite. Today, QPX is being looked into and many questions are still occurring. Although clams in places such as New York are infected, QPX does not cause any damage to humans.