Like nearly every major city in the United States, Philadelphia is suffering from a bedbug epidemic. Unlike other major cities, Philadelphia lacks effective and enforced bedbug policies, enabling infestations to multiply.

The most important thing I’ve learned from a decade studying bedbugs is this: Bedbugs are difficult to eliminate from homes, but they are not so difficult to control in a city. With the proper push, Philadelphia could, in fact, turn the epidemic around.

On Tuesday, a City Council committee had the opportunity to provide that push when it considered a bedbug bill, sponsored by Council member Mark Squilla, that would require landlords to notify tenants about past bedbug issues, develop bedbug control plans, and, most critically, to pay for the treatment of infestations in a timely fashion.

However, at the 11th-hour, Council member Mark Squilla added an amendment to his own bill that shifted costs of treatment to tenants if the infestation is detected after the 90th day of a lease. The amendment is antithetical to the intent of the original legislation and will move the city backward in the fight against bedbugs.

Here is why.

It is extremely difficult to detect a bedbug infestation early on. Bedbugs are small and hard to spot. Their bites are easily confused for ones from mosquitoes, and some people do not react to bites at all. In the dozens of infested homes that I have visited across the city, almost all of them had a well-established infestation before anyone noticed the problem. Once bedbugs invade an apartment, they can spread to neighboring units, making it impossible to discern how, where, or when the problem began.

Here’s a scenario. “Apartment A” has bedbugs. But, out of fear of being slapped with a huge treatment bill from their landlord (on average $1,250), the tenants do not report them. Months pass and the bugs crawl into “Apartment B.” The residents of B, who have lived in the building for years, report the bugs — and are left on the hook for hundreds, if not thousands, of dollars for treatment.

The tenants of A, unable to pay, move out. New tenants come in. The unit is empty, but a couple of bugs are hidden. These bugs lurk there for weeks, quietly grabbing meals when they can. Eventually, a bedbug makes the journey to a baby’s crib in the next room. The parents notice some bites on their child; they look for bedbugs, but these are lodged in the crib frame. The bugs grow up, and they lay more eggs. Finally, the parents see bug feces on the crib. It’s been a year and a half. They are on the hook for treatment costs.

Now, let’s reverse this scenario. City Council passes the original bill that requires landlords to not only disclose bedbug infestations to future tenants, but also to hire a licensed professional for timely and effective treatment. When “Apartment A” tenants suspect they have bedbugs, they tell their landlord. The landlord hires a pest control operator who inspects the unit and adjoining ones. With effective treatment, and a lot of work on the part of the tenants, the bedbugs are eliminated from the building. By taking responsibility for treatment, the landlord has effectively eliminated years of turnover, more infestations, back-and-forth blame among tenants, and future treatment costs.

The savings to landlords are significant, though not immediate. I led a team of scientists in an integrated entomological and economic model of treatment and disclosure policies that was recently published in the Proceedings of the National Academy of Sciences. The study compares the total dollar amount bedbugs inflict on landlords in a city like Philadelphia under disclosure policies — including treatment, vacancy, and turnover costs — compared to a situation without these policies. We found that these policies in fact save landlords money — in just five years. The savings come because disclosure policies have the ability to decrease the prevalence of infestation citywide.

It isn’t impossible to get bedbugs out of a city. We’ve done it before, and we can do it again.

Soon, the full Council will vote on a bedbug bill that, with a two-sentence amendment, has reversed the intent of the proposed legislation. Eight council members had cosponsored the original bill that clearly states that landlords must pay for treatment. I urge the cosponsors of the bill, and the whole of City Council, to demand the original, evidence-based policy. Without the help of City Council, Philadelphia will continue to be known as the “most bedbug infested city in the country.”

Michael Z. Levy is an associate professor of epidemiology at the University of Pennsylvania’s Perelman School of Medicine. He can be reached at mzlevy@pennmedicine.upenn.edu.