As the number of coronavirus cases is again showing an upward trend globally, luxury electric car maker Tesla Inc. CEO Elon Musk said on Monday that he has "supposedly" tested positive for COVID-19 for the second time, but has mild symptoms.

"COVID-19 is the virus of Theseus. How many gene changes before it's not COVID-19 anymore? I supposedly have it again (sigh), but almost no symptoms," he tweeted on Monday.

The Ship of Theseus is a thought experiment that raises the question of whether an object that has had all of its components replaced remains fundamentally the same object. The concept is one of the oldest in Western philosophy, having been discussed by Heraclitus and Plato in 500-400 B.C.

Several coronavirus variants have emerged throughout the world since the coronavirus first emerged in 2019 in Wuhan, China. According to Johns Hopkins University, over 976,000 people have died in the United States from COVID-19.

Last year, Musk had questioned the accuracy of COVID-19 tests after claiming results showed he tested positive twice then negative twice on the same day.

However, Musk has been in support of vaccination. "To be clear, I do support vaccines in general & coronavirus vaccines specifically. The science is unequivocal," he tweeted back in April of last year.