London, England (CNN) -- After a night in a San Francisco motel three years ago, Maciej Ceglowski awoke covered in bedbug bites.
The experience, which he says gave him around 20 large itchy bites and weeks of paranoia, had such a psychological impact on him that he was moved to start a Web site to warn others of the bugs lurking in hotels and apartment blocks across the United States and Canada.
Ceglowski, 34, a computer programmer who now lives in Romania, told CNN: "I realized that there was no effective treatment for bedbugs except avoidance. I thought I could help people by warning them about the dangers and where there are bedbug infestations."
He says his Web site, The Bedbug Registry, now receives between 10,000 and 15,000 visitors daily and up to 100 reports a day of infestations in hotels and apartment blocks, mainly in New York, San Francisco, Toronto and Vancouver.
Ceglowski's battle against bedbugs is part of a wider problem facing urban areas: the rise of pests.
With more than half of the world's population now living in cities, it's a problem that's affecting city dwellers globally and which can pose significant health challenges.
"Fifteen years ago, bedbugs were thought to be history in most developed countries. But they have now bounced back across the world," Clive Boase, a pest management consultant, said.
Bedbug expert David Cain estimates that reports of infestations tripled in UK cities between 2003 and 2007.
The problem has become a global one as bedbugs cross international borders on people and their belongings.
Stephen Doggett, an entomologist at Westmead Hospital, Sydney, reported a 400 percent increase in the number of bedbug samples submitted between 2001 and 2004.
"The data presented here probably only represent the 'tip of the iceberg,'" he wrote in a paper published in the journal Environmental Health Australia.
Cain told CNN that he believes this increase was down to tourists coming to see the 2000 Sydney Olympics.
It's not just bedbugs that are causing headaches. Pests from foxes and mosquitoes to rats, pigeons and cockroaches are thriving in rapidly expanding metropolises.
Increasing urbanization, along with global travel and climate change, are providing rich pickings for these pests.
"Modern city living conditions are pretty attractive to most pests," Boase told CNN. "We produce waste, heat our homes and flush waste into our drains and sewers."
Some pests, such as bedbugs, are an irritation. Others, like rats and mosquitoes, carry disease and pose a major public health risk.
There has been a 33 percent increase in calls to pest companies about rat problems in the last year alone in London, according to Peter Crowden, chairman of the UK's National Pest Technicians Association.
"Since we stopped feeding human food waste to animals, a tremendous amount has ended up in our sewers through waste disposal units," he said.
"I have seen whole chicken carcasses on people's compost heaps, and of course, that attracts rats," Crowden added.
Pigeons and foxes, too, are widespread and can cause public health concerns.
Crowden said: "Pigeons carry the same diseases as rats. Their droppings can also cause respiratory problems."
Foxes have increasingly moved into cities with the availability of food. Their fleas and ticks can be passed to domestic pets.
Crowden told CNN that most pest controllers he knew were reluctant to tackle them, fearing objections from animal rights campaigners. "I stopped dealing with foxes about 10 years ago," he said, "when I started getting death threats."
In areas where there is poor infrastructure, the health risks can be even greater, according to Boase, who advises public bodies, as well as food and waste companies.
"In developing countries, cities are growing very fast as people pour in from the country, and there is often very little urban planning," he said.
With urban populations forecast to swell over the next few decades, the problem doesn't appear to be going away anytime soon.
The proportion of the world's population living in cities will rise to 70 percent by 2050, according to the World Health Organization. By comparison, that figure was 40 percent in 1980.
Each particular urban pest and each particular city has its own individual causes and solutions, Boase said.
In tropical cities, for instance, the biggest -- and fastest growing -- pest is mosquitoes carrying dengue fever, a disease that can be fatal if it's not treated properly.
"Anything that carries so much as a cup of water can provide a habitat for these mosquitoes, and they cause millions of cases of dengue fever," he said.
But the problems across the globe have more similarities than differences, according to Boase.
"Public health and environmental health are seen as rather dirty subjects that people don't really want to think about," he said.
"But it is vital that city authorities pay more attention to public health and pest control, rather than leaving it to private companies who can only deal with each case on its own."