New York City Plague

Jacqueline Fernous

Staff Writer

Most people think about bright lights and a world of opportunity when they envision New York City, but what most do not think about is the garbage and filth littering the streets, especially in rats.

Rats are one of the top animals to spread disease in the city and because of that the New York City Health Department keeps tabs on more than 95,000 rats.

Although the last known plague outbreak was back in 1925 in Los Angeles, the country is trying to maintain its plague-free streak by monitoring the rats that roam New York City every day.

In order to catch these rats and figure out what diseases and lice they are harboring, traps were set up in various locations throughout the city.

Rats are very cautious and aware of their environment, which makes it hard to catch them in traps. If they are trapped, many rats figure out how to get out and then never go near one again. So for scientists it was a patient waiting game for a sample of rats to test. Finally, after 10 months of searching, scientists caught 133 rats to test for disease. They literally had to comb through every rat with a fine tooth comb to discover the 6,500 fleas, lice and mites that lived on the rats.

According to an article on, some lice and mites include tropical rat mites, spiny rat mites, spiny rat lice, and oriental rat fleas.

The thing that alarmed scientists was the oriental rat fleas which are the ones that transmit plague and murine typhus.  Thankfully there was no threat to the rats or people in New York City. A calculation called the Flea Index is used to calculate risk to humans of plague. It’s basically the average number of fleas on a rat. If the Flea Index is below 1 (1 flea/rat), then there is minimal risk of a disease establishing itself in a population.

In 1925, the calculated Flea Index for New York was 0.22. In the newly published study, the flea index was 4.1. That number is alarming to researchers and people living in New York City.

One thing they are trying to figure out still is what bacteria in or on the rats is causing the potential for plague. It is important to know that while right now, the rats pose no threat to the people in New York City, the tests are a precautionary measure used to gauge the amount of threat these rats pose to society. Of the rats sampled, not all rats had fleas and not all areas sampled have rats, so the distribution of rats and disease varies greatly throughout the large city.

One bacterium found was Bartonella, which causes trench fever and several other diseases, but there are many antibiotics around now to cure any disease that someone may contract.

Something that people need to consider now that there is a potential for an outbreak of disease in New York City is to control the amount of litter on the city streets and to try to rat-proof the neighborhood.

People worried about the rats infesting the city will be asked to do their part to make life unpleasant for the creatures. The more difficult they make it for rats to live near humans, the less people will need to worry about a spiny rat louse snacking on their ankles.