America - Andrew Stephen smells a very large rat

Rats - as big as cats and a lot more vicious - are infesting the cities of North America, threatenin

The screams downstairs first alerted me. I had gone to change after an evening out, while downstairs the dog of the household was being released from the kitchen. Then I was breathlessly informed what had transpired: there had been a flurry of activity when Buster, a Cavalier King Charles spaniel never known to have hurt a fly, suddenly started chasing something across the living room. It was not his bone, nor his squeaky hamburger, but a real, live, huge rat. The males of the household, including Buster, then manfully started a search of all nooks and crannies where it could possibly have fled, but the rat had disappeared.

We called Adcock's, a company renowned for cutting off and sealing possible entry and exit points for rodents. They were not at all surprised. "They're all over Georgetown," they said. Widespread though the problem is, few will admit to having it in polite Georgetown society, yet there are now millions of rats in Washington, easily outnumbering the human population. The problem is not limited to the capital. New York recently held a rat summit. Sightings in Chicago have shot up to more than a thousand a day. In Houston, a policeman brandishing a gun furiously chased a rat through a house.

There remained an uneasy feeling in the household that weekend that the rat's entry and exit point into the house could have been the downstairs toilet, a possibility that Adcock's later confirmed. The Norway rat, the kind that is infesting Washington and brazenly walks along the city's pavements in broad daylight, is known to love living in sewers and sometimes takes a swim in and out of toilet bowls in search of food. A lady in Washington named Tira Williams actually got off the toilet, heard some scuffling, put on her glasses to see better, and saw peeking out of her toilet bowl a big Norway rat.

The man from Adcock's - a fellow called Steve - said he had a gut feeling that our rats were, indeed, coming from the sewerage system. He recommended injecting smoke into our sewer pipes - not to kill the rats, as I at first naively assumed, but to see if there were any leakages in the system. Perhaps in the bowels of what, by American standards, is a very old house indeed (c1790) there lay some secret route known only to generations of huge Norway rats? A breeding pair, I was told, will proliferate to 2,000 in a year.

Steve and a colleague got ladders to the roof of the house, and the neighbourhood filled with billowing smoke.

Then - eureka! - they discovered smoke issuing from a hole in part of a crawl space that probably dated back to 1790: Steve thought there had originally been a cesspit there, and that the rats had gnawed their way through pipes and earth. (In my crash course on Norway rats, I discovered that their teeth can exert 24,000lb of pressure per square inch and that they can get through practically anything.) Steve and his colleague concreted up the hole but, just in case, laid rat-traps (like very large mousetraps) laced with their favourite lure: peanut butter.

We thanked Steve and, $750 poorer after he had also nailed up a few possible entry points, assumed our troubles were over. But a few days later, the kitchen garbage started to smell. At least, I thought it was the kitchen garbage. Then gradually, inexorably, the truth started to dawn: I could smell a rat, and a dead one at that.

Torch in hand, I ventured down to the crawl space: there was no sign, only an overpowering stench, of dead rats. I ventured in deeper, only to see, two inches from my eyes, something people do not believe me about when I tell them: a dead rat with a body at least as long as a cat's, and twice as thick. It turns out that these enormous creatures are so strong that when they set off the traps, they fend off the metal recoil like boxers recovering from blows to the head; normally they are so badly hurt, though, that they then wander off to die. Steve came back, and this time he really thinks he has discovered the true hole from the crawl space into the sewers; his colleague put on a spaceman-like uniform and started crawling though 12in gaps. We'll need more smoke to confirm it, says Steve (at $325 a time), but there are no guarantees. "Rats," he says admiringly, "are smart."

The wider problem is, naturally, not at all funny. Rats carry as many as 35 diseases, and are reckoned to have killed more people in the past thousand years than all wars and revolutions combined. But cutbacks in city services are primarily responsible for the rat problems throughout urban America. In 1980, Washington had 140 workers dedicated to catching rats; by the end of that decade there were 22 and, in the 1990s, even fewer. Now the problem has become the great unspoken social ailment of Georgetown, a disease that transcends social and economic boundaries: rats. Big ones.