A single confirmed case of measles can cost a health department close to $300,000, spent before a second case appears and before anyone knows whether there will be an outbreak at all. In 2004, Iowa spent $243,000 to contain one case, and a second case never came.

Outbreaks of infectious diseases are known to be expensive, but researchers had not separated the cost of initiating a public-health response from the costs that rise with case numbers. A new study in Vaccine finds that most of that first bill is fixed: the cost of mounting a response at all, paid the moment a jurisdiction confirms a case, regardless of what happens next. Each additional case then adds about $16,300.

The fixed cost is what makes combating measles expensive out of proportion to its size. Moreover, the fixed cost is what is paid per jurisdiction, not once for the country. Every county or state that confirms a case stands up its own response and pays its own $300,000, whether it ends up with three cases or three hundred. With measles now in 28 Pennsylvania counties , in the worst year since the United States eliminated the disease in 2000, that fixed cost may be paid many times over. As vaccination slips, the first thing that grows is the number of separate places having to respond.

The per-case figure is the less certain of the two. It’s anchored by data from one large New York outbreak. If we ignore that one outbreak, it more than doubles. So it is almost certainly too low a value for most places.

Every figure in the paper is also a floor. It counts no lost wages, no lost schooling and no lost lives. This month two people in Pennsylvania died of measles , both unvaccinated, one an infant, the first American measles deaths in a year and the state’s first in 35 years . That is the unmeasured cost, and no response budget comes close to it. An MMR dose costs roughly $100 at private-sector prices , and often nothing to the patient.