New York, Apr 27 (IANS): A team of scientists from the University of Missouri, in the US, are on the scout for a patient who has been carrying a cryptic strain of the Covid virus for the last two years -- possibly the longest-standing Covid patient ever, according to media reports.

Previously, the longest known PCR confirmed case is thought to be an immunocompromised UK patient who was positive for 505 days with Covid infections.

Led by Dr Marc Johnson, a microbiologist at the varsity, the team said the genetic signature of the strain was greatly different from any existing strain -- which means it can be dangerous if it spreads, Los Angeles Times reported.

Johnson spotted the strain from a wastewater surveillance at a Wisconsin drain servicing 100,000 people. Further investigations revealed that the cryptic lineage is from an individual who was infected almost two years ago.

He believes the strain is being shed by the same person who regularly commutes between Columbus and Washington Court House.

"It's crazy how much virus this person is shedding," Johnson was quoted as saying.

According to the scientist, the strain is a highly mutated version of the SARS-CoV-2 and "unlike anything" experts have seen so far, Daily Mail reported.

"We reverse analyse (wastewater) to see if anything in there doesn't match any lineages," Johnson was quoted as saying.

"Very early on there was this (sample) that was different than anything we had seen.

"If this was circulating, it would immediately be declared a variant of concern," Johnson said.

While it is unclear how the person has harboured the virus for so long, it is likely that the virus has mutated within the patient to the extent that it is not fit to spread.

Instead, the virus has managed to adjust itself in a way that it can live within its host for a long period of time while going relatively undetected, the scientist said.

"There is a good chance they do not know they are affected," Johnson said.

"Whoever this person is, they are apparently still going to work every day and have been for some time," he noted. "It appears that they don't know they're infected. This can't be good for them."

Finding the patient may not only treat but also help scientists gather samples to learn more about the cryptic strain, said Johnson, whose team has been able to track down the holders of cryptic Covid lineages in the past.