For the bubonic plague to spread to humans, it needs at least these three things: rats, a particularly harmful bacteria and enough fleas. Rats in New York City have these fleas, Cornell University scientists recently discovered.
But before you swear off ever visiting the Big Apple for fear of contracting the Black Death, don't - the third puzzle piece is missing. The fleas themselves don't carry the right bacteria to cause the disease, and this pathogen hasn't infected a New Yorker in more than a century.
"The results of our study do not represent an immediate and imminent risk of plague for NYC," Matthew Frye, Ph.D., a Cornell University urban entomologist, told The Dodo. He added, however, this research reinforces the fact that we should "limit contact with [wild] rodents and their ectoparasites."
Frye recently collected 6,500 bugs from the backs of 133 city rats. More than 500 of the parasites, Frye and his colleagues reported Monday in the Journal of Medical Entomology, were oriental rat fleas. In the fourteenth century, these were the likely fleas who bit infected rats, hopped on to Europeans, bit them and then passed on a plague responsible for millions of deaths. (Africa's gerbils, it seems, also acted as a sort of Black Death bank.)
There are a few ways to make sure rats don't feel welcome in your home or workplace, according to Frye. "Sanitation, or housekeeping, is an effective pest management strategy," he said, "because cleaning removes food and water sources used by pests." Another way to keep rodents out of your life is to ensure gaps in buildings, like those around utility lines, are sealed.
We don't need to break up with all urban critters, however. If you spot ants crawling outside along New York's streets, for example, let them go about their insect business. These six-legged custodians are cleaning the city, one cronut crumb at a time.