As many as seven new variants of the coronavirus have been spotted in the United States since the pandemic started, ringing the alarm bells for scientists who think these variants may be more contagious and deadly, US media reports said.

The variants have been detailed in a yet to be peer-reviewed study that was published on Sunday and have each been named after a bird, a New York Post report said.

The mutations have been found by scientists across the country conducting genetic sequencing on positive COVID-19 tests.

However, majority of the COVID-19 cases never go through genetic sequencing so the real extent of the spread is not easy to ascertain.

"I would be quite hesitant to give an origin location for any of these lineages at the moment," co-author of the study Emma Hodcroft told New York Times.

Many questions are still unanswered like how contagious the variants actually are as the data on them is still not sufficient. Other international variants, UK strain being on of them, have been found to be significantly more contagious than the original virus.