Disease, no malaria, zika watch

Please see why you should come and visit Costa Rica

Created: prior to 2018

Malaria, Zika, Dengue fever, Yellow fever, encephalitis, others

Wow, it seems that Mosquitoes are worse carriers of disease than rats.

They are reported as being responsible for making 20% of the world sick every single year.

In the USA, dengue fever and malaria are ‘back’. In Canada we have West Nile Virus.

Like Canada and most of the USA, in Costa Rica, including the Samara, Guanacaste region, mosquitoes are mostly ‘pests’ with a low ‘risk’ of serious illness.

In Canada, we are told to take precautions because, while the risk is low, it is not zero, most of this warning has come in the past years as we’ve had more and more incidences of West Nile Virus, and from my reading about the diseases from mosquitoes in the USA, especially the Southern States, I assume that people there should take precautions too.

But remember, you are going to be outside more – so your risk will be higher because of that factor. And remember, mosquitoes easily bite through thin clothing – especially clothing that is tight against the skin like tight jeans, or anywhere your clothing is ‘tight’ to hold it to your body – such as a waist band if it isn’t very thick.

The most important piece of information in this page is the ‘So what should you do?’ part at the bottom.

So as of October 2019, using various sources, but especially the Canada Blood Services and the CDC:


There is no “locally transmitted” Malaria in Costa Rica. One source says “less than 10 in 100,000” and that is likely due to people coming from Nicaragua or Panama or other countries with the disease – not from catching it in Costa Rica. Note that there is Malaria in nearby countries, such as the East side of Nicaragua, one state in Panama ‘close’ to Costa Rica, and several other states in Panama. While Guanacaste is ‘fairly’ close there is currently no worry in Samara, Nosara, Liberia or really, any other areas of Costa Rica that you might decide to travel to.


There is currently no “locally transmitted” Zika in Costa Rica. But due a variety of reasons, the Canadian Blood society requires that I not give blood for 21 days after I’ve been to Costa Rica. As of writing, there are no Zika outbreaks, but if there is, Costa Rica could become one of the locations.

Dengue: Fairly rare – one report said you are more likely to get it in the Southern USA than in Costa Rica.

Yellow Fever: Not in this part of the world

Encephalitis: About the same risk as the USA.

Irritation. Is there anything of low volume more annoying than a mosquito’s buzz?

Itch: Up until I was about 35 years old, mosquito bites itched and itched and itched. I used gallons of ‘stop-itch’ through the years, and those products only gave me short term relief. But then when I was about 35, I was helping my wife at a kids camp she was running, I counted over 100 mosquito bites (I counted most of them.) on the second day. For years after that, mosquito bites never itched – I guess I built up immunity. But due to travelling and West Nile Virus, and because I hate the sound and site of mosquitoes, I have used more and more insect repellent since that time – and I noticed in 2019 that mosquito bites, the few I did get, were starting to itch a small amount. So I suspect if I keep not getting many, my body is losing its immunity to the itch, and the few I do get are going to be a good reminder to keep using protection against bites.

So what should you do?

Use insect repellents that actually work. (Don’t fall for the Amway skin lotion scam.) For most people, DEET and Picaridin are your best choices. Whichever one(s) you use, apply them often enough.

See for details:

Active Ingredient


Insects Affected


Skin Repellant



Mosquitoes, ticks, some flies

Up to 12 hours


Synthesized pepper plant ingredient

Mosquitoes, ticks, flies

Up to 14 hours

Oil of lemon eucalyptus

Synthesized plant oil


Up to 6 hours


Synthesized plant oil


4-8 hours

Plant oils (soybean, lemongrass, cedar, citronella, etc.)

Natural plant oil

Some mosquitoes

Estimated 30 min. to 2 hours

Clothing Repellents


Synthesized chrysanthemum plant ingredient

Mosquitoes, ticks

Up to 70 washings in pretreated clothing; up to 6 washings when sprayed on; alternatively, it loses effectiveness after 6 or more weeks of outdoor exposure

“Wearable” plant oils (integrated into wristbands or clip-on products)

Natural plant oil

Some mosquitoes (in the vicinity of the wearable item)

Multiple days

Airborne Repellents


Synthesized chrysanthemum plant ingredient


As long as emission device is running (repeller refills lasts 4 hours)

Citronella candle

Natural plant oil

Some mosquitoes

As long as the candle burns

  • A lot of people have concerns about DEET, but as far as I can see, it all comes from mistaking DDT with DEET – two completely different chemicals – completely. DEET seems to, other than water, be one of the most tested and safe chemicals in the world (And the chemical water can kill you if you get too much of it – and you are much more likely to get too much water – drowning – than have any problem from DEET.) The only known ‘complications’ from people with DEET from my research were people who had a pre-condition that made them likely to get the second problem – as a result the evidence is in the direction that the DEET was not the causative agent. Anyway, I know I won’t convince anyone who comes with the opposite opinion, so I’ll stop now.
  • Others have concerns about Picaridin since it is newer and has not had nearly the testing or long term effect that DEET has. But I personally, having read the research, use DEET and/or Picaridin – I have no fears about either of them. See our page on ‘Mosquitoes, Ticks, Flies’ for more information on different options and how effective they have proven to be in tests. Be more vigilant when you see mosquitoes, cloudy days and dusk to dawn.

It is generally agreed that there is no need to sleep in mosquito netting in Costa Rica. If you want to, if you think about it as cool and exotic, fine go ahead, the risk is not considered enough to justify it, but if you are offered it, it won’t hurt. If you do use them, if you want them to make a difference, make sure you tuck them in otherwise they are nearly useless. Mosquitoes will follow the CO2 smell and get in. Note that on TV shows they usually have them hanging down over the sides of the bed – it looks better for TV – but when I’ve traveled in parts of India and other areas that need mosquito netting at night, they do it correctly, not ‘made for American TV.’

Clothing, there are various recommendations about clothing. These seem to me to be the most useful:

  • Wear long sleeved, loosely fitting shirts and pants. Tight fitting allow mosquitoes to bite through. If you use a light material, or a moisture wicking lower level and light, loose outer level, you have the bonus of it being sun protection of SPF 15 or more. And lets be realistic, you are more likely to get a bad sunburn in Costa Rica than illness from mosquitoes.
  • Tuck shirts in or use a loose belt/rope to prevent access to your body that way.
  • Use brightly colored (some say other than yellow) clothing, not dark clothing. And after all, white clothing keeps you cool in the sun.
  • Cotton (including Jeans) and linen don’t prevent mosquitoes from biting through, but many synthetic tight weave, including many high tech sports clothing do.

Other comments and ideas:

  • Stay indoors during from dusk to dawn when mosquitoes are most prevalent.
  • Don’t spray DEET on clothing. Spray it into your hands, then rub it on
    • All exposed skin
    • Ankles, elbows, neck, wrists, forehead (even if under clothing)
    • Anywhere you have tight clothing. (This is not talking about having a tight under layer with a loose outer layer)
  • Stay cool, have showers after you sweat. Besides it feels good too! Mosquitoes are attracted to sweat. Don’t forget to reapply repellent after swimming or showering or sweating heavily.
  • There are several things that increase your CO2 output: Exercise (obviously), drinking alcohol, eating spicy foods, being pregnant, being overweight. Bear this in mind and use more repellent or, if you want, change your habits. But again – not exercising is probably a bad choice for the lesser risk of a mosquito bite in Costa Rica.
  • If you want to try tiki torches and other citronella candles and oils, set them on the ground. Mosquitoes live very near the ground, and the smoke and scent only works if it is between you and the mosquito. This is a ‘why not, every little bit helps’ don’t rely on these as your primary line of defense.

Mosquitoes are terrible at flying

  • You may beg to differ when you are trying to swat them! But a 1mph (2km) wind or higher is enough to keep mosquitoes grounded.
  • Given a choice between a breezy location for your picnic or book reading time and a calm sheltered location, choose the breezy location. (Just be aware: Sunburn! You should probably always apply sunscreen if you are going in the sun, but In a breezy location you are more likely to forget until you have had too much sun exposure.)
  • As a side note, some sources say that the dusk to dawn has nothing to do with the light. It has to do more with dusk AND dawn – at those times of day the wind tends to be less breezy, allowing the mosquitoes to fly
  • If you are outside on a patio and it is calm, why not turn one or two fans on – one for foot level (you don’t want bites there) and one for head/body level.

For those living the life, a few more tips:

  • Clear standing water daily, or just prevent it from accumulating.
  • Plant citronella, lavender, lemongrass, marigolds and/or basil. While this won’t prevent mosquitoes, they will repel some, and you get beauty and nice smell as well. Think of this as ‘every little bit helps’ not as a major solution.
  • You may want to consider spraying. My research says, unless it is done widespread (like at a municipal level) there are better options usually. If you want to consider this, you’ll want to research further before deciding.

And some BAD ideas:

  • Mosquito traps – they lure them from afar. And while they will kill many which makes you think they are doing a good job, studies show they normally lure more into your environment than they kill, so they increase the number around them – which is of course where you are, and mosquitoes are pretty good at sensing you from these devices – they prefer you. But some people swear by them because of how many they kill. Now … if you really want to use them – my thought is buy one for each of your neighbors and get them to turn them on whenever you are outside – maybe that will be effective for you! If you have mosquito breeding grounds and you can put the mosquito trap on the other side (further away from you) then some sources say they sometimes work. But be warned: these traps work by creating CO2, and many politically funded scientists have been saying lately that, after 1000’s of years of consuming CO2, plants are no longer able to and so mosquito traps will cause ‘climate change’ or ‘global ice age’ or ‘global warming’ or any host of other bad sounding things now that plants don’t eat CO2 anymore. So if you use these traps, make sure you find some non-GMO plants (I’m of course sarcastically assuming that older non-GMO plants can still consume CO2, if you didn’t know that the last half of this paragraph was sarcasm, now you do.)
  • Wearing perfume. Any scented perfume, location or soap may attract mosquitoes. So … spraying perfume on someone else in your party may make the mosquitoes on average go for that person, but they will attract more into the area and you will likely get attacked more too.

And it refers a couple times to:

From all my research and personal testing, the available evidence indicates that picaridin and DEET are both effective at repelling black flies, while DEET is more effective at preventing tick bites. Conversely, picaridin seems to be better at repelling other biting insects, notably no-see-ums. Most others are mostly useless or require reapplying every 20 to 6 minutes. Others are only effective while you are applying them (the mosquitoes can’t bite while you are moving your hand along your arm!)