“The response looks to be proportionate to the extent of the problem,” said Justin Wolfers, a University of Michigan economist who has pushed for a large fiscal response to sustain the economy through the virus shutdown. But, he said, “we have no idea what the extent of the problem is.”

The bill includes $350 billion in loans for small businesses to help bridge their expenses for up to 10 weeks. Firms would not need to repay up to eight weeks of the loans if they refrain from laying off employees, or move by June to rehire employees they have already laid off. Supporters of the measure say those loans, if rapidly deployed, could help thousands of firms survive, at least temporarily.

“It is incredibly important that policymakers credibly convince business owners that these conditional loans will indeed be forgiven and that firms’ owners will be treated equitably,” said Stan Veuger, an economist at the conservative American Enterprise Institute. But, he said, “I am skeptical that the size of the package is large enough to cover the entire shutdown-slowdown period.”

The bill also includes $500 billion in aid to airlines and other large corporations that have been hurt by a cratering of consumer demand amid the crisis. Much of the money would be used to backstop loans and other assistance that the Federal Reserve said it plans to extend to companies.

Those programs are in part meant to encourage companies to keep workers on their payrolls. Even if workers are furloughed without pay, the government will essentially step in and assume paying their salaries while the workers continue to be covered by any health insurance provided by their employers.

For workers who lose their jobs, the bill supplies expanded unemployment benefits for up to four months. For many, those payments will match or even exceed the wages they were earning before the outbreak.