Jack Dorsey, Twitter’s chief executive, has pledged to donate $1bn (£800m) to fund coronavirus research to help “disarm this pandemic”.

Dorsey, who co-founded Twitter in 2006 and went on to co-found payments company Square, tweeted on Tuesday that he was donating $1bn of Square shares to a charitable fund, called Start Small, to “fund global Covid-19 relief”.

I’m moving $1B of my Square equity (~28% of my wealth) to #startsmall LLC to fund global COVID-19 relief. After we disarm this pandemic, the focus will shift to girl’s health and education, and UBI. It will operate transparently, all flows tracked here: https://t.co/hVkUczDQmz — jack (@jack) April 7, 2020

Dorsey, 43, said the donation was equivalent to about “28% of my wealth”. Dorsey has a fortune of about $3.9bn, according to the Bloomberg Billionaires Index.

It is by far the biggest single donation to the global fight to tackle the coronavirus pandemic.

Jeff Bezos, the founder of Amazon and the world’s richest person, has said he will donate $100m to food bank charity Feeding America.

“Even in ordinary times, food insecurity in American households is an important problem, and unfortunately Covid-19 is amplifying that stress significantly,” Bezos, 56, said in an Instagram post last week.

Bezos’s donation represents less than 0.1% of his estimated $123bn fortune.

The Bill & Melinda Gates Foundation has given $100m to efforts to develop a Covid-19 vaccine and to fund testing and treatments. Michael Dell, the founder of Dell computers, has committed $100m.

Earlier on Tuesday, the Wellcome Trust called on big businesses to donate $8bn for research into developing diagnostic tests, therapies and vaccines to tackle the pandemic.

Jeremy Farrar, the director of the London-based medical research charity, said a huge investment in scientific research was “the only exit strategy” to save millions of lives and drag the global economy out of an inevitable recession.

Farrar said that while businesses and governments had acted fast to support staff and keep the global economy ticking along, the only long-term solution was to quickly develop vaccines and treatments.

“The only exit strategy for this that I see is the development of diagnostics, therapies and vaccines,” he said. “That’s the only way we can return to normal.”

Farrar told chief executives of the world’s biggest companies that pledging funds to the Wellcome Trust’s Covid-Zero fund “is the best investment your business can make today”.

• This article was amended on 8 April 2020 to clarify that Dorsey co-founded Square.