A brief introduction to the major mosquito-borne diseases.
Malaria is a life-threatening disease transmitted to humans through the bite of parasite-infected female Anopheles mosquitoes. It triggers fever, chills and a flu-like illness which, if left untreated, can lead to severe illness and death. In 2019, malaria caused an estimated 409,000 deaths out of 229 million people infected worldwide. Most of these were children aged under 5 years old mostly in sub-Saharan Africa.
The total cost of malaria control and elimination reached an estimated US$ 3B in 2019.
WHO DataSheet malaria
Dengue is the world’s most wide-spread and fastest spreading mosquito-borne disease. It infects up to 100 million people each year, about 25% of whom become sick, causing around 22,000 deaths.
- endemic in almost 130 countries including parts of US and Europe
- threatens over 40% of world’s population, around 3 billion people
- virus has 4 serotypes, second infections cause life-threatening conditions
West Nile virus (WNV)
WNV is the leading cause of mosquito-borne disease in the continental US. It occurs in almost 20 countries in Europe.
- about 1:5 infections produce fever and other symptoms
- around 1:150 infections cause serious, sometimes fatal, illness
- commonly found in Africa, Europe, the Middle East, Asia and North America
- can be a fatal neurological disease in humans
- In 1999, imported WNV led to a major outbreak in the continental USA
- widely established from Canada to Venezuela
The most recently emerged mosquito-borne viruses, Zika causes no or only mild symptoms in most people infected – but can cause severe neurological defects in the developing fetuses of pregnant women. This can lead to babies being born with microcephaly (a rare disorder in which a baby’s head is much smaller causing developmental problems that can sometimes be fatal).
- appeared in Pacific region in 2007
- exploded in Brazil in 2015, spreading rapidly through Latin America
- with no previous exposure people had no immunity to the virus
- occurs in Central & South America, the Caribbean, Africa, Asia, & Pacific Islands
- in US it has been spread locally in the states of Florida and Texas
- 2019 saw the first local outbreak of Zika in Europe
This virus is not yet spreading in the US, but almost 800 people in 44 states contracted the disease while traveling. In Europe its first outbreak was in Italy in 2007.
- an alphavirus, carried by Aedes mosquitoes (primarily Aedes aegypti)
- originated in tropical Africa, spread east to Asia and north into Europe
- now occurs in over 60 countries in Asia, Africa, Europe, and the Americas
- over 1.7 million suspected infections in Americas by 2016
While many with yellow fever virus show no symptoms, others commonly suffer fever, headache, muscle pain and nausea. A small percentage, however, enter a more severe phase – about half of whom will die.
Fortunately, a safe and effective vaccine exists against yellow fever. The main challenge is to vaccinate people in affected areas fast enough to contain the spread. It is also hard to stockpile enough vaccine to face an outbreak; it currently takes up to one year to produce additional doses.
- not currently occurring in US or Europe, but remains a threat
- has caused deadly outbreaks in Brazil, Angola and DR Congo
- is now endemic in many countries in Africa, Central and South America
- risk of deadly outbreaks in heavily populated areas with high mosquito densities
- human populations often have little or no immunity (as is currently the case in Africa)
* Caraballo, Hector (May 2014). “Emergency Department Management Of Mosquito-Borne Illness: malaria, dengue, and West Nile virus”. Emergency Medicine Practice.