San Francisco, Health screenings, limiting density, and ensuring strict adherence to social distancing are some of the measures that Apple said it has taken in its global supply chain to address COVID-19's challenges, and to ensure people are able to return to work safely.

Apple said it is working with its suppliers around the world on a range of protections suited to the circumstances in each country.

These details were revealed in Apple's annual "Supplier Responsibility Progress Report" released on Thursday which also included a letter from Sabih Khan, Apple's Senior Vice President of Operations.

"We put people first in everything we do -- and require everyone we work with to do the same -- because we want to uphold the highest standards," Khan said in the letter.

"We're requiring the use of personal protective equipment -- both during work and in all common areas -- and have worked together to implement enhanced deep cleaning protocols and deploy masks and sanitizers," he added.

Apple said it has partnered with suppliers to redesign and reconfigure factory floorplans where needed and to implement flexible working hours -- including staggered work shifts -- to maximise interpersonal space.

"We continue to work closely with leading medical and privacy experts to develop advanced health and safety protocols," Khan said.

The 'Supplier Responsibility Progress Report' which is a look back at the progress it made last year said that 19.4 million supplier employees were trained on workplace rights since 2008.

Apple said its health and wellness education training programme expanded to Vietnam, joining China and India.

Over one million supplier employees have received training through the programme, it added.

As part of its "Responsible Sourcing" programme, the "Salmon Gold" project developed new mining methods while achieving habitat restoration.

Apple said it is pioneering the use of blockchain technology to trace Salmon Gold from the mine to its supply chain.