A latest study has found that rats in New York City carry a flea species that is capable of transmitting plague pathogens, including the bubonic plague, typhus and spotted fever.

The study, conducted by teams from Cornell and Columbia Universities, included 133 New York City rats and found 6,500 fleas, lice and mites that can carry bacteria that can lead to serious diseases in humans.

Matthew Frye, lead author and Cornell entomologist, said that the Oriental rat fleas, which are notorious for their role in spreading the bubonic plague, were also among the rats that were found by them.

He mentioned that just a single flea bite can pass on infection as the fleas regurgitate rats' infected blood and guts when they bite into human hosts, passing along disease.

According to a 1925 study, one out of five rats carry a flea, but the Cornell/Columbia study has found an average of four fleas on a rat. The study mentioned that some of the rodents carried around two dozen of the little bloodsuckers.

The study said that with the advancement in the modern medicine New Yorkers no longer need to worry about an outbreak of the Black Death, but at the same time, the fleas are carrying other viruses that should be monitored. The study reported that some of the fleas also carried Bartonella pathogens.

Cadhla Firth, co-author of the study, said, "These pathogens can cause a wide range of clinical syndromes, some severe".

Fyre said that during the research they studied three areas, including a residential building, a mixed-use building and an outdoor space. Different levels of rats, fleas and bacteria, were distributed in these areas which indicate that there is a need of more research to see just where the disease is hiding.