Commodities started falling steadily after China reported its first death from the coronavirus in January and began taking steps to curb its spread, slowing the country’s economy early in the year. While stocks held up well at that time, materials fell because China is a critical source of demand, accounting for about half of global consumption of some commodities like copper.

As the virus has spread to other countries, from Italy to South Korea, commodities have fallen alongside global stocks, sending the S&P 500 down 13% in the past seven trading sessions. The pain has extended to agricultural commodities including sugar and cotton.

The broad selloff is a major concern for some analysts because commodity prices can provide a real-time indicator of activity in the world economy. The current slide reflects slumping demand and bloated inventories, a recipe for excess supply. Some investors worry the widespread selling of assets associated with risk also portends more pain ahead for stocks.

“We know there’s going to be continued volatility,” said Shannon Saccocia, chief investment officer of Boston Private, which has been maintaining a smaller position in stocks than the benchmark it tracks. “With this uncertainty, you’re not really sure what the best place to hide would be.”