Health care workers like Dr. Spencer know that it is in their interest to ensure that — if symptoms do arise — they get care quickly to improve their chances of survival and to reduce the risk of infecting their friends and families. Dr. Spencer reported his temperature promptly when it was a low-grade fever of a 100.3 degrees and was rushed to Bellevue Hospital Center for isolation and treatment while his fiancée and two friends were put into voluntary isolation.

Fortunately, for the public, there are clearer heads at the federal level than there are in the statehouses of New York and New Jersey. On Monday, strict new federal monitoring rules, announced by the Centers for Disease Control and Prevention last week, went into effect for travelers entering the United States from Guinea, Liberia and Sierra Leone. The rules are designed to avoid the confusion of state-by-state policies, give health workers and other travelers a clearer idea of what to expect and reassure the public that somebody is in charge. State and local health departments will contact travelers daily for 21 days after their departure from West Africa to check on their temperatures and other symptoms (21 days is the maximum period for symptoms to develop). If the returning health care workers fail to report as required, health officials will track them down using contact information they have provided upon entry.

The C.D.C. further refined this approach on Monday with additional guidelines recommending how people with direct exposure to Ebola patients or burials should be handled. A doctor at high risk of Ebola because he was exposed to a patient’s bodily fluids would be strongly advised — and, if necessary, even ordered by health authorities — to avoid traveling or congregating in public.

The problem with a mandatory quarantine, even if done at home, is that it can discourage heath care workers from volunteering to fight the virus at its source in West Africa. Doctors Without Borders, the nongovernmental organization that has led the battle there, typically sends its workers on arduous four- to six-week assignments. The risk of being quarantined for another 21 days upon return has already prompted some people to reduce their length of time in the field and may discourage others from volunteering in the first place.

An editorial published Monday in The New England Journal of Medicine cited estimates that tens of thousands of additional volunteers will be needed to control the epidemic and warned that a mandatory 21-day quarantine, for people who are not sick and may never become sick, would be “more destructive than beneficial.” Policies that will reduce the chances of recruiting additional volunteers — without actually protecting the public — will only make the Ebola crisis worse.