What living thing is most dangerous to humans? Sorry Shark Week, it is not the Great White Shark; it is the mosquito! In fact, “mosquitoes kill more humans worldwide in five minutes than sharks kill in a year.” (Borenstein, 2002) Many public health researchers believe 50% of the people who have ever lived, died due to a disease transmitted by a mosquito bite. (“Malaria”, 2016) (Merrill, 2005) In addition, mosquito-borne diseases have killed more people than all wars in history combined. (“Mosquitoes and disease”, 2016) The elimination of malaria has been such a high, global public health priority, that since 1902, five Noble Prizes have been awarded for scientific work associated with the eradication of this deadly disease. Despite intense public health efforts for centuries, malaria remains the most deadly disease in history. Why? The persistent, pervasive mosquito!
The recent outbreak of the Zika virus has brought new attention to the need for global mosquito control. (Hayes, 2016) However, mosquito control has been a global public health crisis dating back thousands of years. Despite worldwide public health efforts, both today and for the past two centuries, it is estimated that 500,000 people continue to die every year from mosquito-borne diseases, primarily malaria. (“Malaria”, 2016) According to World Health Organization (WHO), there were 214 million cases of malaria worldwide in 2015, with 438,000 deaths, mainly among children under 5 years of age in Sub-Saharan Africa. (“World Malaria Report”, 2015)
500,000 people continue to die every year from mosquito-borne diseases
Malaria is the classic, mosquito-borne disease caused by a parasite that has been a scourge for centuries, with descriptions of the disease going back at least 4,000 years (” History of Malaria”, 2016). Although there are over 3,500 species of mosquitoes, only one, the female anopheles mosquito, is responsible for spreading malaria. (” History of Malaria”, 2016) The U.S. Centers for Disease Control (CDC) was established in 1946 with the principle purpose of mosquito control due to malaria. Malaria Control in War Areas- MCWA – was the predecessor of the CDC.
The CDC and U.S. public health measures were so successful that malaria was declared to be eliminated in the U.S. in the early 1950’s. (” History of Malaria”, 2016) Today, there are typically 1,500-2,000 cases each year in the U.S., mainly from travelers or immigrants from Africa or South Asia. (CDC, Malaria, 2016) Around the world, however, WHO estimates that today there are 3.2 billion people at risk of malaria transmission in 106 countries and territories. (“World Malaria Report”, 2015)
Malaria has been referred to as a “disease of poverty”. “Every two minutes, a child from Africa dies from malaria.” (“Malaria”, 2016)
Although malaria has been basically eliminated in North America, we are at risk for it being reintroduced, because the mosquitoes responsible are still prevalent. There have been 63 outbreaks of malaria in the U.S. between 1957 and 2015. (“History of Malaria”, 2016)
West Nile Virus
Another potentially deadly disease today, spread by mosquitoes, is the West Nile Virus. West Nile Virus has been detected in many species of mosquito. In this disease, people get infected when they are bitten by a mosquito that has fed on an infected bird, not another person. (” West Nile Virus”, 2015) The results are the same: a potentially deadly disease virus is spread by a mosquito bite. The majority of cases, 80%, are mild, with no signs and symptoms. Others only have a mild fever and headache that goes away without medical intervention. However, 20% of cases result in severe headache, fever, disorientation and overall weakness, requiring immediate medical attention. (” West Nile Virus”, 2015) These cases can last quite a long time. In very rare cases involving West Nile Virus (1 in150 cases), severe neuro-invasive infections may develop, including encephalitis and meningitis. Encephalitis is an inflammation of the brain and is very serious and life threatening. Meningitis is a disease that also involves inflammation of the membranes (meninges) that protect the brain and spinal column, and it is also very serious and life threatening. (” West Nile Virus”, 2015)
The West Nile Virus has not been eradicated and has, in fact, spread throughout the 48 continental states in the U.S. since the first outbreak in the summer of 1999. The West Nile Virus kills about 100 Americans a year. There are no medications or vaccines to treat or to prevent West Nile Virus. The West Nile Virus is also prevalent today in Africa, Asia, Europe and the Middle East. (“West Nile”, 2015)
Yellow fever is a viral infection transmitted by the bite of infected Aedes or Haemagogus species mosquitoes, found in tropical and sub-tropical areas, such as South America and Africa. (” Yellow Fever”, 2016) This virus can damage the liver and other internal organs and is potentially fatal. There is no known specific treatment and it is highly recommended for people traveling to be vaccinated for Yellow Fever prior to traveling to infected areas in the world. (“Yellow Fever”, 2016)
Dengue Fever is another serious infection the is the result of exposure to the bites of the Aedes aegypti species of mosquito. It is a leading cause of illness and death in the tropics and sub-tropics around the world. The CDC estimates that 400 million people are infected annually. Dengue fever is rare in the U.S., but is epidemic in Puerto Rico, Latin America, Southeast Asia and the Pacific Islands. There is no known cure or current vaccination available. The only known prevention is to avoid mosquito bites. (“Dengue”, 2016)
Chikungunya Fever is yet another disease where a virus is transmitted by a mosquito. Symptoms include fever and joint pain. This is not typically a deadly disease, but the symptoms can be quite severe. There have been outbreaks in Africa, Asia, Europe, and in countries bordering the Indian and Pacific oceans. The first case in the Americas was documented in 2013 in several Caribbean Islands. There is no known cure, treatment or vaccination available. The mosquito responsible for spreading the disease, Aedes aegypti and Aedes albopictus species, are also capable of transmitting dengue fever and the Zika virus. (“Chikungunya”, 2015)
Zika Virus Fever
Zika virus is currently generating the most anxiety and concern about mosquito infections. (Hayes, 2016) Several world famous athletes have refused to participate in the upcoming Summer Olympics in Brazil due to the fear of the Zika virus. Most people that are infected by Zika will only experience mild symptoms, such as slight fever, rash, joint pain and red eyes. However, there is now a documented scientific link between the Zika virus and birth defects in babies born to infected mothers (Dyer, 2016) and Guillain-Barré Syndrome (Cao-Lormeau, 2016).
The Zika virus, spread by the bite of the female Aedes aegypti mosquito, has now been confirmed to cause microcephaly, which results in small heads and brain damage to newborn babies of infected mothers. The mosquito thought to be responsible for spreading the Zika virus in Brazil was initially thought not to be a concern in North America. However, the Zika virus has now spread to the “Asian Tiger” mosquito, whose range is now as far north as New York and New Jersey, and will likely soon be seen throughout most of North America. On July 21, 2016, Brazilian researches said they found evidence of Zika virus in another species mosquito, the Culex quinquefasciatus. More testing is required to determine if this mosquito is capable of actually transmitting Zika to humans. If they can, the implications are troubling, as the Culex is a much more common species of mosquito than the Aedes and can survive in temperate climates. (Prada, 2016)
There are now documented cases of the Zika virus and babies born with microcephaly in the U.S., but those cases involved pregnant women being exposed in known countries at risk outside the U.S. (Hayes, 2016) This week, the CDC was informed of four cases of Zika virus infection in the State of Florida. These cases are believed to have been contracted in the Miami area from Aedes aegypti mosquitoes. If confirmed, these would be the first cases of Zika contracted in the continental United States from mosquitoes. (“Florida Investigation”, 2016)
Protective Measures Against Mosquito-borne Illness
There are steps that individuals can do to protect themselves and their families.
- The simplest advice is to avoid areas known for mosquitoes at all costs. The danger time for mosquitoes is between dusk and dawn (just like sharks!)
- Eliminate all sources of standing or stagnant water which is a potential breeding ground for mosquitoes. This means clean swimming pools, rain gutters, bird baths, flower pots, pet bowls, old tires, buckets and other items where water can collect such as tarps, pool covers and boat covers.
- Look for potential leaks around air conditioners and anywhere water puddles may form.
- Do not leave windows open without properly fitted screens and, by all means, close the door.
- Wear protective clothing when outdoors, especially between dusk and dawn, such as long sleeves, long pants, shoes and socks, and a hat.
- Cut the grass and eliminate weeds in your yard.
- Use commercially available products, such as insect/mosquito repellent and devices designed to attract and kill mosquitoes.
- There are also little fish, known as minnows, that eat mosquitoes and their larvae in fish ponds on or near your property.
- Ask your local authorities what they are doing about mosquito control, in general, and the Zika virus, in particular, such as draining local swamp land.
- Report any other areas of standing water in your neighbourhood.
- Practice safe sex, including the use of condoms, as Zika can be transferred to sexual partners.
Great progress is being made in the fight against Malaria with the help of international agencies and global public health campaigns focusing on insecticide-treated bed nets or ITNs. ITNs provide simple, but effective, prevention as part of an overall global public health effort, including antimalarial treatment and indoor residual spraying. The CDC reports that the use of ITNs has reduced childhood deaths from all causes by 20% in Africa. (“Nothing but Nets”) These ITNs allow people to sleep with protection from mosquitoes in their peak hours, dusk to dawn. Organizations such as Malaria No More and NothingButNets are conducting fundraising and global education campaigns in cooperation with the United Nations.
Novel approaches to mosquito control, including the development of genetically-modified mosquitoes, introducing bacteria to mosquitoes to prevent eggs from hatching and sterilizing male mosquitoes, are all being considered in the effort to eradicate mosquito-borne illnesses (Dockrill, 2016)
While no one would advise swimming with sharks, the fact remains that the mosquito presents a much bigger danger to humans than the menacing, toothy fish. Knowing the risks and protecting yourself from them are your best defense against these tiny vectors of disease.
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