So you want to be a coronavirus contact tracer? Johns Hopkins has a class for that.

Hunting down people exposed to the coronavirus and quarantining them is seen as a vital step in controlling its spread, and now Johns Hopkins University has created a free online course to turn people of all backgrounds into a nationwide force of hunters.

The course for so-called contact tracers was specifically created for the state of New York, which plans to quickly hire thousands of the workers. But officials expect the six-hour class and assessment to be used by health departments around the country and maybe the globe to stem cases, particularly after states begin to reopen.

“We can’t stop all transmission, but it’s still an important effort to keep cases low,” said Emily S. Gurley, an infectious disease epidemiologist in Hopkins’ Bloomberg School of Public Health and the course’s lead instructor. “Every little bit is going to have an impact.”

Hopkins had previously released a report finding that 100,000 tracers would be needed nationwide, at a cost of about $3.6 billion for a year. In the absence of a federally coordinated effort to conduct widespread testing and tracing, the report said the effort would have to be done by states and local governments.

Most local health departments already employ some tracers, who regularly find those with all kinds of infectious disease from tuberculosis to sexually transmitted diseases. They are considered a crucial — but understaffed —backbone in the quest to find people who have been exposed to COVID-19, the disease caused by the coronavirus.

Officials at the Maryland Department of Health had recently said they had about 200 to 250 tracers but Monday said the goal is to have 1,000 tracers in the state. Half will work at local health departments and the other half will work at a call center run by an independent institution at the University of Chicago called the National Opinion Research Center.

Recruitment began two weeks ago, and officials say there already are 1,000 applicants. The officials say they are working with local departments on staffing needs, and expect those departments to initiate tracing within 24 hours of receiving lab results. State officials expect federal funding to pay for some of the work.

Massachusetts was the first state to report a massive effort to hire large numbers to do the tracing. Now, New York is doing it.

The Hopkins course was paid for by Bloomberg Philanthropies, and it is designed for people with at least a high school diploma.

The course has five modules designed to provide basic information on the virus and how it’s transmitted; fundamentals of contact tracing, including how to identify cases and their contacts; steps involved in investigating cases, including simulated interactions with the public; ethics of tracing, including balancing privacy and public health considerations and use of technology; and skills for effective communications and how to build trust.

After someone tests positive for COVID-19, they are asked to identify people they may have come in contact with so they can be contacted. They are also told to quarantine for 14 days, a “big ask” which means not leaving the house and means monitoring for symptoms.

The tracers can help link them to support services.

Gurley, an associate scientist in the Hopkins Center for Global Health, said every person does not have to be found and quarantined for the tracing effort to be helpful. Every infected person passes the virus to an average of two to three people, so interrupting some of the transmission slows the spread. “If we stop one or two new infections, we’ve prevented a lot of cases down the line,” she said. “It’s not all or nothing.”

Dr. Joshua M. Sharfstein, Hopkins’ vice dean for public health and community engagement, gave a demonstration Monday of the course, which uses actors to help illustrate how conversations between tracers and the public may go.

The program is expected to have 6,400 to 17,000 tracers in New York. Sharfstein said 400 people in New York have registered for the course. Anyone can take the course, including those who intend to work as a tracer and those interested in how the process works.