Malaria, the most widespread mosquito-borne disease, affects 350-500 million people each year. Dengue Fever infects nearly 400 million people each year, causing an estimated 25,000 deaths and an enormous economic cost in affected countries, which rivals that of Malaria. Other serious illnesses transmitted by mosquitoes are on the rise. Chikungunya, Yellow Fever and Eastern Equine Encephalitis are painful and debilitating diseases which can in some cases prove fatal; all are increasing in prevalence.
Although Malaria is transmitted by several different types of mosquito, Dengue Fever is primarily passed on by just two related species, called Aedes aegypti (the Yellow Fever Mosquito) and Aedes albopictus (the Asian Tiger Mosquito). Both of these mosquitoes also transmit Chikungunya, Yellow Fever as well as several other viruses, making these tiny insects some of the most dangerous creatures on the planet.
Dengue Fever is the fastest-growing mosquito-borne disease. It is a serious and sometimes fatal condition, which affects nearly 400 million people every year. Read more about this dangerous illness, and how Oxitec is working to control it, in the Dengue Information Centre.
Zika is a flavivirus, transmitted primarily by Aedes mosquitoes. The virus was originally identified in Uganda in 1947, and the first major outbreaks occurred in the Pacific, on Yap Island in 2007 and French Polynesia in 2013. In 2015 an outbreak was reported in Brazil, which has since spread to a large number of countries in the Americas, as well as some Pacific Islands.
Some areas with Zika outbreaks have reported an increase in babies born with microcephaly as well as an increase in Guillain-Barré syndrome, a disorder in which the body’s immune system attacks its nerve cells. According to the WHO, there is growing evidence that Zika virus may be the cause of these disorders. Because of the increased incidence of these disorders in areas of Zika outbreak, the WHO declared a Public Health Emergency of International Concern on February 1 2016.
According to the CDC, many people infected with Zika do not show symptoms so may not know that they have the virus. When symptoms do occur, they are usually mild and last for a few days to a week. Symptoms include fever, skin rashes, conjunctivitis, muscle and joint pain, and headache.
In addition to transmission via the Aedes mosquito vector, sexual transmission of Zika virus has been described in certain cases, and the presence of the Zika virus in semen has also been found.
There is currently no vaccine for Zika, so control of the mosquito and avoidance of bites are the best ways to combat the disease.
Chikungunya is a rapidly emerging viral disease that is also spread by the Aedes mosquitoes. According to the Centers for Disease Control and Prevention (CDC), symptoms of chikungunya infection include fever, headache, fatigue, nausea, vomiting, muscle pain, rash and joint pain. The joint pain can last for months. On rare occasions, infection may lead to viral encephalitis and death. Because there is no vaccine or specific treatment available, the best way to avoid chikungunya infection is to minimise the likelihood of contact with an infected mosquito.
There have been recent large outbreaks in India and South East Asia but the geographical spread is increasing and is of growing concern to health officials. On the island of La Réunion in 2006, over 20% of the population was estimated to have been infected. There was also an outbreak in Europe in 2007 in Northern Italy. The virus is believed to have been introduced into Italy by a vacationer from India and then transmitted by local mosquitoes. During the outbreak, there were 254 suspected and 78 laboratory-confirmed cases including one death. Because only a small percentage of infected individuals present for diagnosis, the actual number of cases may be higher. This outbreak has forced global public health experts to re-evaluate the geographic threat of this mosquito-borne virus.
Yellow fever occurs in Africa and Latin America and used to be known as ‘Yellow Jack’ among European sailors who visited the tropics. Once in a community it can spread rapidly. It is characterised by fever, muscle pain, headache, nausea and vomiting. Most patients improve and the symptoms will disappear but in some the disease becomes ‘toxic’. There is high mortality once the disease has entered the toxic phase.
There is no cure for yellow fever but there is a vaccine making monitoring and rapid vaccination critical in stopping the disease once an outbreak occurs. However it is expensive and availability is not sufficient to protect other parts of the world if the disease should move there from Latin America.