We slap them, we spray them and they keep coming back. The pesky mosquito. There are over 3000 different kinds of mosquito, with 200 of those choosing to chomp down on humans for their fill of blood. Surprisingly, these tiny insects are associated with the most deaths out of all the animal kingdom. This comes from their ability to carry and spread a nasty variety of deadly diseases.

Many cases diagnosed in the U.S. are people who have travelled to tropical or subtropical countries where local transmission is common and have returne from their travels with it. Let’s have a closer look at what makes these little creatures carry that make them capable of being so lethal.


Most commonly in tropical and subtropical areas, chikungunya is transmitted via the mosquito. Three to seven days after being bitten by an infected mosquito, the patient may begin to display the following symptoms:

  • Fever
  • Muscle ache
  • Swelling and pain in joints
  • Developing a rash
  • Headache

It is common for patients to get well again after one week, but some may suffer joint pain in the following months. Those who are at the highest risk with this disease are adults who are over 65 years, new-borns that are infected around the time of birth and patients with pre-existing medical conditions.


Dengue can come from one of four closely-related dengue viruses. This means the disease can be contracted more than once, with the patient being far sicker when suffering a second time.

Although the majority of patients recover within a week or two, severe dengue presents complications that can be deadly. To soothe pain and control fever, the infected person should take acetaminophen but stay away from the likes of ibuprofen or aspirin.

To diagnose dengue, the patient should have a high fever and two or more of the following symptoms:

  • Pain in the joints
  • Rash
  • Pain in muscles (or bone pain)
  • Headache
  • Eye pain, or pain behind the eyes
  • Bleeding mildly (for example, petechiae which are small red spots on the skin, bruising easily or bleeding from the nose or gums)
  • A low count in white blood cells

The signs of severe dengue are seen as the patient’s temperature begins to subside. This is normally three to seven days after symptoms first appeared. 

Look out for:

  • Vomiting persistently, or pain in the abdomen
  • Patches on the skin or spots
  • Bleeding from the gums or nose
  • Blood in vomit
  • Black and tarry faeces
  • Easily irritated and drowsy
  • Clammy, pale and or cold skin
  • Struggling to breathe

If any of these symptoms are present, immediately see a health care provider or visit an emergency room.

Eastern Equine Encephalitis (EEE)

Eastern Equine Encephalitis (EEE) is a viral illness, which some birds, along with horses and equine species can die from. The virus is managed by treating its symptoms, as there is no treatment or vaccine for EEE yet. Depending on different factors, EEE can be responsible for either systemic or encephalitic illness.

Check for:

  • Pain in joints and muscles
  • Chills
  • Fever

This may turn into:

  • Vomiting
  • Convulsions
  • Disorientation
  • Headache
  • Coma


Both serious and potentially fatal, malaria is caused through parasites spread through mosquitos, although pets and animals will not get sick from it.

The main symptoms are:

  • Chills and shaking
  • Aching muscles
  • Tiredness
  • Fever

Treating malaria can vary depending on the factors involved. Sometimes it will be treated with antimalarial drugs, but factors like age, weight, location and pregnancy can change the options a person may have available to them.

St. Louis Encephalitis (SLE)

A mosquito carries the virus for St. Louis Encephalitis when it feeds on infected birds. It will not make either sick, but the infected mosquito then passes the SLE virus on to the person it bites. Those infected may have no symptoms or a fever while being mildly ill. The symptoms include:

  • Headache
  • Fever
  • Feeling nauseous
  • Vomiting
  • Drowsiness

Often this can progress to:

  • Confusion
  • Disorientation
  • A stiff neck
  • Feeling dizzy
  • Tremors
  • Coma

It takes 5-15 days before symptoms show, but they present themselves quite suddenly. S humble proportion of people, mainly infants and the elderly, can develop encephalitis. Care for SLE is based on treating symptoms, as there is no vaccine to prevent, nor specific medication to treat the illness.

West Nile Virus

A variety of animals, as well as birds, horses and people, can be infected with the West Nile Virus. Thankfully, it cannot be passed from person to person. Many who are infected will not show any symptoms, but those who do have either one of the two different forms this disease can take. These are:

  • West Nile fever
  • West Nile Neuroinvasive disease

WNND tends to be more severe in its symptoms, compared to WNF. Only 1 in 150 people will be diagnosed with the more severe illness. Very rarely will a person die from it, and the mild disease may only last a few days.

Symptoms for WNF include:

  • Headaches
  • Fever
  • Backache
  • Rashes
  • Aching body
  • The lymph glands are swollen

WNND symptoms include:

  • Headaches
  • Stiff or sore neck
  • A high fever
  • Feeling disoriented
  • Tremors and convulsions
  • Weakness in the muscles
  • Paralysis
  • Coma

Western Equine Encephalitis (WEE)

This viral illness is spread to people and horses through the bite of a mosquito that is infected. The majority of those who are infected do not become ill, but some may have mild illness and fever. Encephalitis can develop in a small handful of those infected, particularly young children and the elderly. This can be life-threatening and requires the patient to be hospitalised.

Symptoms of WEE:

  • A high fever
  • Headache
  • Neck stiffness
  • Feeling weak
  • Vomiting

This can progress to:

  • Feeling disoriented
  • Being irritable
  • Seizures
  • Coma


The same type of mosquito to transmit dengue and chikungunya viruses are also known to spread the Zika virus to people. If a pregnant woman is infected, she can pass this on to the unborn baby as well, causing birth defects and developmental delays. It can also be passed on through blood transfusions or sexual contact.

The symptoms include:

  • Pain in the joints
  • Red eyes (conjunctivitis)
  • Fever
  • A rash which may be itchy

There is no vaccine or treatment for Zika, meaning it is advised to practise safe sex as well as to avoid being bitten by mosquitos in countries that the virus is common.

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