China has changed its criteria for diagnosis, prompting a large increase in reported infections and deaths last week. Tests for the virus have not been very accurate, and people who do not seek or receive medical care may not be counted. And people with mild or no symptoms may not realize they have the virus and may not get counted, either.

Researchers in Germany presented evidence on Tuesday that people who have the new coronavirus can infect others even when they have no symptoms, as disease experts had suspected. Their findings, published in a letter in the New England Journal of Medicine, indicated that people may be spreading the disease before they know they are sick.

But the Chinese government’s daily tally of new infections and deaths from the virus has declined steadily since Feb. 12, a trend that could offer a glimmer of hope if it persists.

On Tuesday, the authorities reported that in the previous 24 hours, 1,886 new cases had been confirmed — the first time since Jan. 30 that the number had dropped below 2,000. On Wednesday, the number of new infections reported by authorities was again below 2,000, with China recording 1,749 confirmed new cases of coronavirus infection, bringing the country’s total number of reported infections to 74,185.

With 136 deaths reported in Wednesday’s figures, the total number in China of those confirmed to have died from the virus surpassed 2,000, reaching 2,004.