The bed bug: what it is and why it is back

What it is

The bed bug (Cimex lectularius L.) feeds only on blood, usually human, biting at night while the sleeper lies still. It neither flies nor jumps: it walks, which is why it almost always reaches a new place carried by people.

It transmits no known infectious disease, which is part of why it was long written off as a nuisance. The harm is real and of another kind: itchy bites, allergic reactions, and a psychological toll the literature states plainly — anxiety, nightmares, hypervigilance, insomnia, loss of self-esteem. It is now treated as a public-health matter.

Where it concentrates

Infestations are not evenly spread. They build up where many people live in close contact, turnover is high and personal effects come and go constantly — that is, in communal settings.

• Care homes and nursing homes — the problem is twofold here: among over-65s living in a confirmed infestation, 42% report no reaction to the bites at all. The commonest warning sign does not arrive late — it does not arrive, precisely where residents are most vulnerable.
• Reception centres, dormitories and homeless shelters — high turnover, shared space, luggage in constant motion.
• Prisons and boarding schools — close cohabitation and shared furniture, with little scope for isolation.
• Hospitals and healthcare facilities — where the bill is not just the treatment: at one Cleveland hospital each infestation cost between $125 and $1,050, totalling almost $56,000 in a year.
• Public and low-income housing — the literature is blunt: socially disadvantaged people bear the greatest impact, and poor communities become reservoirs for the insect.

This is why the bed bug is not a private problem: those who carry the heaviest burden have the fewest means to deal with it, and the duty to catch it falls on whoever runs the building.

How to recognise it

The adult is dark brick-red and 6 to 8 mm long, females larger than males. Unfed, its body is oval and strongly flattened — the shape that lets it slip into cracks a few millimetres wide. After a blood meal it swells, the outline rounds out and the colour turns deep red.

The signs of an infestation

The bed bug is nocturnal and elusive, so you rarely see it. What you see are its traces, concentrated in harbourages within a few metres of the bed.

• Digested-blood spotting — black or brown specks on sheets, mattress seams, bed-frame joints and the headboard. This is the most reliable sign.
• Cast skins — the translucent moults nymphs leave behind at every stage.
• Eggs — cream-white, just over 1 mm, glued into cracks.
• Bites — in rows or clusters on uncovered skin. On their own they prove nothing, and not out of caution: 54% of people show no reaction to their first bites, and early on the reaction can take some ten days to appear. It becomes near-immediate only after repeated exposure — by which time the infestation is established.

The life cycle

Each female lays 200 to almost 300 eggs in total, in the same crevices where the colony shelters by day.

• Egg — cream-white, just over 1 mm; it hatches in 7–10 days at room temperature, in about 8 at 25 °C.
• Nymph — five stages, each needing a blood meal to reach the next. Without food development stretches out enormously, but the nymph does not die.
• Adult — with plentiful food roughly 7 weeks take it from first nymphal stage to maturity.

Temperature runs everything: cold slows development, while above 45 °C the insect cannot survive. Yet it endures starvation for months, even over a year — which is why simply leaving an infested room empty solves nothing.

The comeback, and its arrival in Italy

From the 1950s reports collapsed worldwide, and for half a century the bed bug all but disappeared from the scientific record; the decline is credited to better post-war conditions and to residual insecticides such as DDT. Since the 1990s it has been back, with infestations rising year on year. The most widely accepted causes are the growth in travel, the second-hand trade and above all insecticide resistance: resistance is documented to pyrethroids, carbamates, organochlorines and, more recently, organophosphates.

In Italy the first infestations described in the literature date to the summer of 2003: two separate cases in Pisa, both with circumstantial evidence pointing to international travel. One of the two patients developed a severe bullous eruption — a reminder that "carries no disease" is not the same as "harmless".

The European picture confirms the resurgence: Belgium recorded a 30% rise in cases over summer 2023 against 2022 and German control work grew 93% between 2019 and October 2023, while in France online interest quintupled over the decade 2013–2022, peaking with the media wave of autumn 2023. That peak deserves caution, though: through the scare, searches for how to actually treat an infestation stayed below 2% of the total — fear travelled faster than the cases did.

How it spreads

The bed bug cannot fly and walks slowly: on its own it would go nowhere. We are what moves it.

• In luggage — the main route: it slips into the seams of suitcases and rucksacks and travels with the guest, from one property to the next.
• In second-hand goods — used furniture, mattresses and bed frames can bring in an established colony.
• Between adjoining rooms — inside a building it travels along skirting boards, conduits and cavities, moving from one room to the next.

This is why the reported room is almost never the only problem: on a first positive, the adjoining rooms must be inspected too.

Why finding it early matters

An early infestation is a handful of insects hidden in cracks a few millimetres wide, and visual inspection struggles to find them. That is this insect's paradox: exactly when treatment would cost least, the problem is hardest to see.

In a communal setting the delay is structural on top of that: you wait for the sleeper to report it, but if the sleeper is an older resident who barely reacts to bites, that report comes once the colony has already spread from the bed into the furniture and the neighbouring rooms. Catching it early confines treatment to one room rather than a floor, and cuts the time beds stay out of use.

How it is treated

Eradication is integrated and combines several tools. Heat is the main lever, because it leaves no residue and reaches every life stage:

• Heat — the bed bug does not tolerate 45 °C, and at 50 °C every stage dies, eggs included. Linen should be washed above 55 °C; steam kills eggs too.
• Vacuuming — lifts bugs and eggs out of cracks; the bag must be sealed and disposed of at once.
• Chemical treatment — targeted on harbourages and repeated: at room temperature eggs hatch in 7–10 days, so the second pass belongs inside that window.

The outcome has to be verified later, with traps and repeat inspections: calling an infestation solved without checking is the commonest way to see it come back.