Mosquitoes live everywhere. There are thousands of species and about **200 in
the United States**. Female mosquitoes bite animals and humans and drink a
very small amount of blood — they need its protein and iron to produce eggs.
Afterwards they find standing water and lay them there; the eggs hatch into
larvae, then pupae, then adults. Males live about a week to ten days, females
up to several weeks, and some females **hibernate through winter and live for
months**.
Why a bite itches
Most bites are harmless. The **itchy bump is an immune system response to the
mosquito's saliva**, not to the loss of blood, and it usually goes within a
day or two. That is the most common reaction.
Less commonly, the saliva causes an allergic reaction — blisters, large
hives, and in rare cases anaphylaxis, a whole-body allergic reaction and a
medical emergency.
And then there is the reason mosquitoes matter at all: **they spread
diseases**. Many have no treatment and only a few have vaccines.
What they carry, and where
| Disease | What it does | Where it is |
|---|---|---|
| Chikungunya | Fever and severe joint pain, usually about a week — joint pain can last months | Most US cases are imported; a few have spread within the country |
| Dengue | High fever, headaches, joint and muscle pain, vomiting, rash; most recover in weeks, some cases become life-threatening | Rare in the US |
| Malaria | A parasite: high fevers, shaking chills, flu-like illness. Life-threatening, but treatable with drugs | A major problem in tropical and subtropical regions; almost all US cases are imported |
| West Nile virus | Often no symptoms; usually mild fever, headache, nausea. Rarely enters the brain and becomes life-threatening | Has spread across the continental United States |
| Zika virus | Often no symptoms; one in five get a mild fever, rash, joint pain, pink eye. Spreads mother to baby in pregnancy, causing serious birth defects, and between sexual partners | A few outbreaks in the southern United States |
These are more of a problem in Africa and other tropical regions, and **more
of them are spreading to the United States**. One reason is **climate
change**, making parts of the country more favourable to certain mosquito
species; the others are increased trade with, and travel to, tropical and
subtropical areas.
Prevention
Repellent. Use an EPA-registered insect repellent — registration means
it has been evaluated for safety and effectiveness. Check it contains one of:
DEET, picaridin, IR3535, oil of lemon eucalyptus, or para-menthane-diol.
Follow the label.
Cover up. Long sleeves, long trousers and socks outdoors. **Mosquitoes bite
through thin fabric**, so spray thin clothes with an EPA-registered repellent
such as permethrin — on the clothes, never directly on skin.
Mosquito-proof the house. Install or repair window and door screens, and
use air conditioning if you have it.
Remove the breeding sites. Empty standing water regularly: flowerpots,
gutters, buckets, pool covers, pet water dishes, discarded tyres, birdbaths.
This is the step that reduces the mosquitoes rather than the bites.
Before travelling, find out whether there is a disease risk where you are
going and whether a vaccine or medicine exists for it. See a provider familiar
with travel medicine 4 to 6 weeks before the trip.
Source: MedlinePlus, U.S. National Library of Medicine.
Licence: CC0 1.0 (public domain) · Adapted from medlineplus.gov
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