A Number 10 source has confirmed that Mr Cummings is the latest member of the Downing Street inner circle to either be diagnosed with Covid-19 or be forced to self-isolate as a result of symptoms associated with the deadly virus.
Boris Johnson, Health Secretary Matt Hancock and the UK's Brexit negotiator, David Frost, have all been struck down with coronavirus, while chief medical officer Professor Chris Whitty has quarantined himself after noticing symptoms.
Mr Cummings, the mastermind behind Vote Leave's messaging at the EU referendum, was last seen running out of Number 10 shortly after Mr Johnson posted a video message on Friday announcing he had tested positive.
A Number 10 source told the PA news agency that the 48-year-old noticed symptoms of Covid-19 over the course of the weekend and had decided to self-isolate.
He will continue to stay in contact with the Downing Street team while in isolation, the source added.
As of Sunday, there were 19,522 positive cases in the UK and 1,228 of those admitted to hospital with Covid-19 had died.