Bed bug infestations are on the rise - and the pests are hard to kill

For nine months, Ms He (full name withheld) and her two children woke up every morning covered with excruciatingly itchy bite marks. When they realised they were caused by bed bugs - highly invasive, hard to eradicate pests - the mental torment began.

"For the kids, it was a much more serious problem, because the bed bugs focus on the children. My daughter does not want to sleep on her own, and now all three of us sleep together [in the bottom bed of a bunk bed]," says He, a 40-year-old single mother. She and her six-year-old boy and 10-year-old girl live in a 70 sq ft subdivided flat in Kwai Chung.

Hong Kong's bed bug problem is growing. Statistics provided by the Food and Environmental Hygiene Department show the number of complaints of bed bugs has been rising, from 29 in 2011, to 47 in 2012, and 79 in 2013 (as of November). Of those cases, 34 per cent came from Sham Shui Po, and just 5 per cent were from Hong Kong Island.

William Hung, the chief executive of Johnson Group, a local pest control firm, says the volume of bed bugs cases he's handled has risen sharply in the past five years. His firm handled 105 cases in 2009 and more than 500 last year. Bed bugs are a common problem for people living in public housing estates, because of the population density.

The small wingless insects were once a major domestic problem worldwide. Their prevalence declined with the widespread use of DDT from the mid-20th century. But there seems to be a recent resurgence of the blood-sucking insect globally, says the department.

International travel, immigration, changes in pest control practices, and insecticide resistance may have contributed to the resurgence in developed countries, say researchers from the University of Mississippi Medical Centre, who published a report in the journal JAMA on the health and medical effects of bed bugs, and control and eradication strategies.