Tiger mosquito in Portugal: how to recognise it, why it is dangerous and what to do at home
In September 2026 the tiger mosquito was found in Castelo Branco, and half the country rushed to look up what an “espécie invasora” is. There is no need to panic: this mosquito has lived on the mainland since 2017, in eighteen years of surveillance not a single virus-infected mosquito has been caught on the mainland, and the one thing that really depends on you is not leaving it water in your garden or on your balcony. Below, in order: how to tell it from an ordinary mosquito, where it has already been found and since what year, what it carries and what it does not carry yet, how to protect yourself and what it costs, where to report a sighting, what to do about a bite and when to see a doctor. Madeira is covered separately: a different mosquito of the same genus lives there, and in January 2025 there really was local transmission of dengue.
What happened and why everyone is talking about this mosquito now
On 14 September 2026 the local health service, ULS Castelo Branco, announced that a mosquito of the species Aedes albopictus — the one known as the tiger mosquito — had been found in the concelho (municipality). It was not found by chance: there are traps across the country belonging to the REVIVE network, run by the health institute INSA and the health authority DGS together with local public health services. The service made it clear at once that the find was expected: the species is already known in several parts of the country. We wrote about it in our press round-up for 14 September — “Tiger mosquito found in Castelo Branco”.
The news spread because it contained an unfamiliar phrase — espécie invasora, “invasive species”. There is nothing frightening behind it: that is the name for an animal or plant that people have brought to a place where it did not live before and where it has settled. This mosquito comes from the tropical forests of South-East Asia and has spread around the world over the last thirty years in two ways: in old tyres, which always hold a little water, and in ornamental bamboo. In Europe it was first found in Albania in 1979 and in Italy in 1990, and it is now on the list of the world's hundred most harmful alien species.
For Portugal this is not 2026 news. The species has lived here since 2017 and takes over new municipalities year after year: in 2024 it was recorded in 18, in 2025 already in 28. So the right question is not “has it arrived” but “what should I do about it” — and the answer is short, it is in step six.
“Oh come on, even pensioners speak English here. We rented a flat for 900 — a T2, and over there it was 1,500+. There's no air conditioning in flats at all, it's +28 at night and the bed turns into a frying pan, the tiger mosquitoes are eating us alive and no Raptors help. Shops already close at 8, some at 7.”
Translated from Ukrainian; the original is at the linkukrporto06.03.2023
What it looks like and how it differs from an ordinary mosquito
The tiger mosquito is small and strikingly black and white: a dark body with silvery-white spots on the legs and body. The main feature specialists use to identify it is a single silver stripe down the middle of its back, that is, the top of the thorax. ULS Castelo Branco described it the same way: dark, with a white stripe along the head and the top of the thorax, the body and legs banded in white and black.
Local mosquitoes can have contrast too, but it is brownish and yellowish rather than black and white. The honest conclusion is this: the species can only be identified for certain under a magnifying glass, and at REVIVE that is done by entomologists. Identifying it at home “by eye” goes wrong all the time.
The second clue is the time and place of the bite. The ordinary mosquito that whines over your bed bites in the evening and at night. The tiger mosquito bites during the day, usually outdoors, flies in low and quietly, and goes for the legs and elbows. It also comes indoors: in Rome, females full of blood were found precisely inside buildings.
The third clue is distance. It does not fly far, about 200 metres. If a mosquito like this is biting you in your garden, it bred in that same garden or in your neighbour's over the fence — and that, by the way, is good news: getting rid of the water in your garden is within your power.
“We don't live by the river, we're in the Bonfim area, we've got a little garden. Sat out there all summer - not a single mosquito buzzed past”
Translated from Russian; the original is at the linkchatporto23.10.2022
Where it has already been found and since what year
Everything below comes from the annual REVIVE reports, not from newspapers: in retellings, the year the species appeared in each region keeps shifting.
The North — 2017. The first find in the country was at a tyre retreading plant in the municipality of Penafiel. Since 2020 the mosquito has been found outside that industrial estate as well, and in 2024 for the first time in Gondomar and Valongo.
The Algarve — 2018. At first only Loulé. In 2020 Faro was added — traps around the outer perimeter of the airport, in 2021 Tavira, Olhão and São Brás de Alportel, in 2022-2023 Albufeira. By 2024 there were ten municipalities, from Alcoutim and Castro Marim to Lagoa and Vila Real de Santo António.
The Alentejo — 2022. Mértola, at first as eggs; in 2023-2024 eggs and adult mosquitoes in Serpa. A single find in Portalegre in 2024 remained the only one: it has not been seen there since.
Lisbon and the Tagus Valley — 2023. In September an alert about a find came in, and it was confirmed in the municipalities of Lisboa and Oeiras. In 2025 there were four municipalities: Lisboa, Oeiras, Almada and Sesimbra.
The Centre — 2024. In 2025 the species extended its range to Condeixa-a-Nova and Covilhã, and on 14 September 2026 it was found in Castelo Branco — that is after the latest report.
In total, in 2025 — 28 municipalities against 18 in 2024, 41,314 eggs in special traps and 19.5% of all adult mosquitoes caught, against 10.5% in 2018-2024. The species is also trapped separately at points of entry: on the outer perimeter of Faro airport, at the same tyre retreading plant in the north and at the international coach station in Lisbon — in other words, it keeps being brought in.
And a warning straight away: you cannot judge the tiger mosquito by how much you are being bitten. Where there are clouds of mosquitoes, they are most often ordinary species from marshes and irrigated fields, and where there are almost none, the tiger mosquito may be living in two abandoned buckets behind the house.
“We're in the south of Portugal There are veeeeeeery few mosquitoes. We sit outside in the garden in the evenings no problem. Windows are open at night too without screens - I've very rarely seen mosquitoes.”
Translated from Russian; the original is at the linkschoolinportugal15.08.2022
What makes it dangerous — and what does not, yet
On its own, a bite from this mosquito is just a bite. The danger lies elsewhere: the species can carry the dengue, chikungunya and Zika viruses, as well as Dirofilaria — parasites that mostly affect dogs. In Europe it has already proved this: local chikungunya outbreaks in Italy, local dengue cases in France and Croatia.
For a bite to pass on a disease, two conditions are needed at once: the mosquito must be able to carry the pathogen and it must be infected. An uninfected mosquito does not pass on disease, however painfully it bites.
So what about Portugal. In 2025 REVIVE tested 5,261 mosquitoes of six species — three times as many as the year before. One pool of nine mosquitoes came back positive, and they were not tiger mosquitoes from the mainland but Aedes aegypti from Madeira (more on that in step twelve). Not a single tiger mosquito from the mainland carrying dengue, Zika or chikungunya has been found since 2017. In the Algarve and on Madeira, insect-specific flaviviruses have also been found — they live only in mosquitoes and do not matter to humans.
Hence the careful wording from ULS Castelo Branco: mosquitoes of this species “may carry viruses”, but “so far not a single virus-infected mosquito has been detected in the country”. The second statement is true for the mainland; on Madeira infected mosquitoes were in fact found in January 2025, and that is worth bearing in mind when reading such announcements.
“I won't recommend a doctor, but I'll just mention (just in case) that I once thought my husband had malaria, and it turned out to be Dengue. Which is worse... Malaria is just treated with quinine. Unfortunately there's dengue in Prt too, even though we hardly know about it.”
Translated from Russian; the original is at the linkchatporto11.01.2026
What dengue is and what the symptoms are
Dengue is a viral disease that is passed on only through the bite of an infected mosquito: it does not spread from person to person. According to DGS, symptoms appear 3-7 days after the bite, 14 at the latest: fever, severe headache, muscle and joint pain, nausea and vomiting, red spots on the skin; less often it leads to bleeding. The illness rarely lasts more than ten days, but the weakness afterwards drags on for a long time.
An important correction to the fears: according to figures cited by the Madeira health service, 40 to 80% of infections cause no symptoms at all. Fewer than 5% of cases are severe, and children and teenagers have the hardest time.
There are four serotypes of the virus, and immunity remains only to the one you have had. That is why a second infection with a different serotype can be more severe than the first — this is not a scare story from the chats but the reason dengue is considered a serious disease.
Dengue cases are diagnosed in Portugal every year, and almost all of them are imported: a person caught it in the tropics and arrived already carrying the virus. For the mainland this means one thing: if you come back with a temperature, tell the doctor where you have been (step ten).
“I had it in Thailand when I was 31. Spent a week completely flat out, thought I'd die from the temperature or cough my lungs up, whichever came first. Second week it was like ordinary flu or covid. Then it passed. Took some local pills specifically for dengue, but can't remember the name now.”
Translated from Russian; the original is at the linkchatporto15.01.2026
What to do in your garden and on your balcony
This is the main step of the guide, and also the most boring one: the tiger mosquito needs no marsh or pond — it breeds in small pools of standing water close to where people live. A saucer under a flowerpot, a forgotten bucket, a tin can, an old tyre or a bottle cap is enough. The Madeira health service says it plainly: the female lays her eggs in clean water with plant debris and will use even bottle tops and eggshells.
What ULS Castelo Branco and INSA ask you to do:
1. Empty and clear away anything where water collects: flowerpots and the saucers under them, buckets, cans, tyres, discarded rubbish. Either remove saucers or turn them upside down. 2. Cover barrels, wells and watering containers — so that a mosquito cannot get in. 3. Clean and treat your pool, and when it is not in use, cover it or drain it. 4. Clean drains and gutters: a caleira clogged with leaves is a ready-made breeding site. 5. Keep rubbish bins closed. 6. Scrub pets' water and food bowls with a brush once a week. 7. Tyres — take them for recycling or keep them dry under cover: it was in tyres that this mosquito came to Portugal. 8. Put fish in an ornamental pond: they eat the larvae.
Two points without which the clean-up is pointless. First, once a week: it takes 7-14 days from egg to adult mosquito, so doing it once a month achieves nothing. Second, wash, do not just empty: the eggs are stuck to the side above the water, survive drying out for almost a year and then come to life with the first rain.
“Mosquitoes need standing water. Marshes, ponds or lakes with no outflow etc. Where there aren't any, there aren't any mosquitoes. And wind helps a lot too.”
Translated from Russian; the original is at the linkru_Portugal_pt22.04.2023
Screens, air conditioning, repellents: what really helps
DGS lists the measures that work briefly: skin repellent with 30-50% DEET or with IR3535, reapplied to all exposed skin every four hours; clothing that covers the body, not too thin and also treated with repellent; if you like, treating clothes with permethrin; screens on windows and doors and over the bed; air conditioning, because mosquitoes do not fly in the cool. INSA adds picaridin and oil of lemon eucalyptus to the same list.
The order is this: first keep the mosquito out of the house, then everything else. A window screen costs less than any spray and works round the clock; in the chats people repeat this year after year.
About ultrasonic repellers and wristbands: they are not on the DGS or INSA lists at all, and in parents' conversations they have failed. A plug-in vaporiser with tablets and insecticide spray in the room do work, but that is chemicals in the air, and with a baby or a pet in the house they are usually the last choice.
Separately, about children and pregnant women: the age from which a repellent can be applied is written on the packaging itself, and at the pharmacy they will choose one to suit the age — that is what people in the chats do, rather than guessing from the ingredients. For a baby, a net over the cot and long-sleeved clothing are more reliable than any product on the skin.
“The most effective thing is not letting mosquitoes into the flat Mosquito screens on the windows solve the problem. There are special screens for balcony doors too”
Translated from Russian; the original is at the linkpequenos_PT17.05.2026
“We've got an ultrasonic mosquito thing from Chicco too, it plugs into the socket. The effect is basically zero it doesn't work on our mosquitoes 🤷♀. No idea why.”
Translated from Russian; the original is at the linkpequenos_PT01.10.2025
Where to report it if you see one of these mosquitoes
There is no official “report a mosquito” desk in Portugal, and it is worth knowing this in advance so as not to waste time looking for one. There are three ways that work.
Your local public health service. Mosquito surveillance on the ground is run by the Unidade de Saúde Pública (public health unit) of your ULS — the same service that announced the find in Castelo Branco. That is who you call if the mosquito has appeared in your municipality or if there is abandoned standing water nearby that nobody is dealing with.
MosquitoWeb. A platform of the Institute of Hygiene and Tropical Medicine at NOVA University: the “Reportar achado” (report a find) form asks for the location on a map, whether you saw it indoors or outdoors, where exactly, your name and phone number, and asks for a photo. It also has a map of confirmed finds across the country. This is a university “citizen science” project, not a government service: it collects sightings and checks them, but it does not make decisions about your garden.
CEVDI, INSA's vector laboratory. The Centre for Vectors and Infectious Diseases Research in Águas de Moura, phone 265 912 222, email cevdi@insa.min-saude.pt — the address and phone number are printed in the institute's own leaflet. These are the people who identify the species under a magnifying glass.
What a report achieves. After a confirmed find the response plan is stepped up: extra traps are set and the catches are collected more often. Madeira shows what this looks like in numbers: in January 2025, 17 extra traps were set around the homes of the two people who fell ill, within a radius of 250-500 metres. In Castelo Branco, the ULS also announced it was stepping up its plan.
How real people go about it we cannot say: in all the years of our chats there is not a single account of someone reporting a mosquito or of what they were told. Screens and repellents come up every summer, species surveillance never.
And what not to expect: a van coming to spray the street with chemicals. The Madeira health service says plainly that spraying insecticides from vehicles and aircraft is expensive and ineffective — adult mosquitoes come back. Only getting rid of the water works.
Bitten — what to do
With an ordinary bite it is simple: do not scratch, apply something cold and, if you like, put on an after-bite gel from the supermarket or pharmacy. For insect bites, INEM gives the same general advice: ice on the bite, keep the limb still, and in serious cases see a doctor.
The tiger mosquito's bite itself is no worse than an ordinary one, but it bites during the day and a lot, and in people with sensitive skin the mark can last for weeks. This is normal and goes away on its own; if every bite swells up and will not heal, that is a case for a dermatologist, not a mosquito problem.
When to go beyond the pharmacy:
1. You have a temperature. 2. Redness is spreading around the bite, the spot is hot, pus has appeared — this is what an infection brought in by scratching looks like. 3. A child has bites all over the body and they are keeping them awake. 4. You have come back from the tropics and a temperature appeared within the first two weeks — that is the next step.
The first port of call in Portugal is the pharmacy: the pharmacist will choose an ointment and tell you whether it is worth going to the centro de saúde (health centre). The 24-hour SNS 24 line is 808 24 24 24, and they will also decide whether you need an appointment. Signs of a severe allergic reaction — swelling of the tongue and throat, shortness of breath — mean 112; they are covered in detail in our guide “Asian hornet in Portugal”, and how to call an ambulance is in “Ambulance and emergency care”. With a mosquito bite this is rare, but it is worth knowing where to call.
“The pharmacy just gave me the same spray. They said without a temperature or a large affected area there's not much point going to the saúde. We'll see in the morning, depending on how it is. Thanks so much”
Translated from Russian; the original is at the linkpequenos_PT31.03.2026
“Oh, turns out I'm not the only one getting bitten to bits ;))) I never had this problem, but last autumn every mosquito bite swelled up and itched for ages.Got as far as a dermatologist, they gave me a cream (can't find the name right now) - it helped quickly, but I had to put it on new bites too. And then it went away again, so I think it's some combination of factors that sets it off + stress.”
Translated from Russian; the original is at the linkpequenos_PT05.06.2026
Back from the tropics with a temperature — tell your doctor
This is a case where more than your own health depends on you. Dengue, Zika and chikungunya reach Portugal with people: someone caught it in a country where the disease circulates all the time and arrived with the virus in their blood. If the tiger mosquito lives in their municipality, local transmission can follow — which is exactly what happened on Madeira in January 2025.
DGS's advice is simple: if after a trip you develop a fever, diarrhoea, vomiting, skin or breathing problems, see a doctor — they will check for malaria, dengue, rickettsiosis, leptospirosis and more. According to the same source, about 8% of people who fall ill on a trip need treatment.
At the appointment, mention three things: where you were, when you got back and when the temperature started. Without this, a fever after the tropics looks like an ordinary cold, and nobody will order a dengue test. In the first days of the illness it also makes sense to protect your household from bites: sleep under a net and do not sit out on the balcony in the evening — the period when you can infect a mosquito is short, a few days.
Dengue vaccine: what exists and who needs it
A dengue vaccine does exist. Qdenga was authorised for sale throughout the European Union on 5 December 2022; according to the EMA's description it is given to adults, adolescents and children from the age of four, in two doses. In a study of 20,000 children it reduced fever from confirmed dengue by 80% and hospital admissions by 90%.
In the chats there is a condition going around that “it's only given to people who have already had it”. The Qdenga description contains no such condition: the EMA mentions only age. The restriction from the chats applies to a different, earlier vaccine, and the two are easy to mix up.
Do you need it? For living on the mainland — no: there has never been local dengue transmission here, and protection from bites matters more than any vaccine. Talking about the vaccine makes sense before a trip to a country where dengue circulates all the time, and that conversation should happen at a travel clinic appointment — consulta do viajante — where they look at your itinerary, dates and what you have already had.
And a warning about sources. The DGS dengue page is out of date on two counts: it says that Aedes mosquitoes have not been found on the mainland (they have been found since 2017) and that no vaccine exists (it has existed since 2022). Checked on 14 September 2026. You cannot rely on it on these two points; on the symptoms of the disease it is still fine.
“There are WHO-approved vaccines against dengue and malaria. You need to ask your family doctor or at the consulta do viajante. Better to get the dengue one, coz reinfection with a different serotype can be much more serious. They don't give malaria jabs to ordinary mortals in Portugal, I think.”
Translated from Russian; the original is at the linkchatporto15.01.2026
“The dengue jab is only given if you've already had it once. They don't give it to people who haven't had it”
Translated from Russian; the original is at the linkchatporto15.01.2026
Madeira is a different story
Madeira is home not to the tiger mosquito but to its relative Aedes aegypti, and this is the most efficient dengue carrier in the world: it bites almost exclusively humans, breeds in small man-made containers, rests inside houses and rarely strays more than 50 metres from homes.
How it got there. The species was identified by the Funchal Natural History Museum in 2005, after residents of the parish of Santa Luzia had long complained of itchy bites from an unfamiliar mosquito. Seven years later, from 26 September 2012 to 3 February 2013, the island had a dengue outbreak — the first in Europe since 1928. Today the mosquito is present in all the municipalities on the south of the island, most densely in Funchal, Câmara de Lobos, Santa Cruz, Ponta do Sol and Calheta; in Porto Moniz it was recorded once and did not establish itself.
What happened in January 2025. Dengue virus serotype 2 was found in mosquitoes caught in Funchal: one positive pool of nine mosquitoes. The virus was sequenced in full, and it matched the virus in one of the two people who fell ill on the island — so the transmission was local. Judging by its relation to Asian samples, the virus was brought in at the end of December 2024. There were few mosquitoes at the time and the weather did not help transmission, so the outbreak went no further: no new infected pools were found. For REVIVE this was the first find of a dangerous arbovirus in all eighteen years of surveillance.
What this means for a trip. Nothing frightening and no “don't go”: ordinary protection from bites — repellent, clothing, screens, air conditioning — deals with it. This mosquito bites during the day, peaking early in the morning and a few hours before sunset, and goes for the legs and elbows, so it makes sense to put repellent on them and not just on your arms. If you live in a house with a garden — the same saucers, buckets and gutters as on the mainland.
On Madeira you can report abandoned water or rubbish where mosquitoes breed to IASAÚDE through the “Não Mosquito” platform — its address is given by the regional government's own website.
“We once stayed there in a little house, in a shady garden, in Funchal on Estrada Monumental. Ants crawled in everywhere 😱 and the mosquitoes ate us alive. August-September.”
Translated from Russian; the original is at the linkPortugal 🇵🇹 TravelAsk chat16.02.2023
“Hadn't even thought about mosquitoes, though I'm flying to Madeira in a few days. Read loads of articles and blogs, nobody ever mentioned this problem…”
Translated from Russian; the original is at the linkPortugal 🇵🇹 TravelAsk chat01.04.2023
What not to do
Do not spray your garden and bushes yourself. Chemicals kill adult mosquitoes for a few hours, and a day later new ones arrive from the same puddle. The Madeira health service, which has experience of an outbreak, says so plainly: spraying insecticides is expensive and ineffective because the hit on adult mosquitoes is too short-lived. The only thing that reduces their numbers in the long run is getting rid of the water.
Do not wait for someone to come and sort it all out. The municipality is responsible for public spaces, but the breeding site in your saucer will only be cleared by whoever empties it.
Do not confuse the tiger mosquito with the gnats around your plants. The tiny flies that hover over flowerpots are fungus gnats; they live in damp soil and do not bite at all; when the soil dries out, they disappear too. Similar flies are found in drains and on overripe fruit, and the ways of dealing with them are different.
Do not panic about dengue on the mainland. Infected mosquitoes have never been found here; there are cases of the disease, and they are imported. The sensible response to news of a find is to walk round your garden and empty out the water, not to look for symptoms in yourself.
Do not buy ultrasonic devices. Neither DGS nor INSA mentions them, and in the chats they have not worked for anyone. The same money spent on a window screen works round the clock and without electricity.
“You need to work out what kind of midges they are: there are ones that breed in the drains, ones in flowerpots, ones on fruit if it's been lying around and starts to go off a bit etc. The ways to deal with them will be different.”
Translated from Russian; the original is at the linkchatsetubal24.06.2024
What to bring
- A photo of the mosquito, if you managed to swat it and take a picture: without one the species cannot be identified, and the MosquitoWeb form accepts it
- The exact address and what is nearby — a garden, balcony, building site, abandoned plot: the sighting is linked to a place on the map
- CEVDI (INSA) phone and email: 265 912 222, cevdi@insa.min-saude.pt — this is where the species is identified
- The SNS 24 line number — 808 24 24 24, and 112 for a severe reaction
- Repellent with 30-50% DEET or IR3535 and after-bite gel — from the supermarket or pharmacy
- Screens for windows and the balcony door: cheaper and more reliable than any product on the skin
- Your travel dates, if you are coming back from the tropics: where you were, when you got back, when the temperature started
Where people most often trip up
- The tiger mosquito bites during the day and outdoors, the ordinary one in the evening and at night: the time of the bite is the first way to tell them apart
- You cannot identify the species by eye: the giveaway is a silver stripe down the middle of the back, and it takes entomologists to check it
- It flies about 200 metres: if it bites you in your garden, it bred in your garden or your neighbour's
- A saucer under a flowerpot or a bottle cap is enough for it; it does not need a marsh or a pond
- A container must be washed, not just emptied: the eggs are stuck above the waterline and survive drying out for up to a year
- Once a week, not once a season: it takes 7-14 days from egg to mosquito
- Virus-infected mosquitoes have never been found on the mainland; on Madeira they were found in January 2025
- Dengue cases in the country are imported — but if you arrive with the virus and this mosquito lives nearby, local transmission can follow
- Ultrasonic repellers and wristbands do not appear on the DGS and INSA lists
- Spraying insecticides from vehicles and aircraft does not work: adult mosquitoes come back
- The DGS dengue page is out of date: it says there are no Aedes mosquitoes on the mainland and that no vaccine exists
- In the chats the dengue vaccine is described by the rules of the earlier vaccine — the Qdenga description has no “only for those who have had it” condition
- There is no official “report a mosquito” desk: you call your Unidade de Saúde Pública, or write to MosquitoWeb or CEVDI
- Tiny flies over flowerpots are not this mosquito and do not bite at all
How it went for people
“They said scabies, then a sun allergy”: how mosquito bites were treated for months as the wrong thing
A mother told a parents' chat how a run of bites on her son ended: the child was bitten all over in a few nights, everything swelled up and itched until it bled, at A&E they suspected scabies and prescribed treatment, then a dermatologist said it was a sun allergy, and the family started keeping the child out of the sun. Neither helped, and it turned out to be ordinary mosquitoes. It all ended with three screens — on the window, the balcony and the door. June 2026.
Retold in our own words from messages in open chats. The link leads to the full original message.