When properly treated, people with malaria can usually expect a complete recovery. However, severe malaria can progress extremely rapidly and cause death within hours or days. In the most severe cases of the disease, fatality rates can reach 20%, even with intensive care and treatment. Over the longer term, developmental impairments have been documented in children who have suffered episodes of severe malaria. Chronic infection without severe disease can occur in an immune-deficiency syndrome associated with a decreased responsiveness to "Salmonella" bacteria and the Epstein–Barr virus.

During childhood, malaria causes anemia during a period of rapid brain development, and also direct brain damage resulting from cerebral malaria. Some survivors of cerebral malaria have an increased risk of neurological and cognitive deficits, behavioural disorders, and epilepsy. Malaria prophylaxis was shown to improve cognitive function and school performance in clinical trials when compared to placebo groups.

Liver dysfunction as a result of malaria is uncommon and usually only occurs in those with another liver condition such as viral hepatitis or chronic liver disease. The syndrome is sometimes called "malarial hepatitis". While it has been considered a rare occurrence, malarial hepatopathy has seen an increase, particularly in Southeast Asia and India. Liver compromise in people with malaria correlates with a greater likelihood of complications and death.

More than 90% of the global burden of visceral leishmaniasis (VL) is contributed by six countries: Bangladesh, Brazil, Ethiopia, India, South Sudan and Sudan. In India, more than 70% VL cases are reported from the state of Bihar. North Bihar, India (including Araria, Purnea, and Kishanganj) is the endemic zone of this disease.The disease is endemic in Iran including Ardabil, Fars, North Khorasan...

But, while the disease's geographical range is broad, it is not continuous. The disease clusters around areas of drought, famine, and high population density. In Africa, this has meant a knot of infection centers mostly in Sudan, Kenya, and Somalia. Living conditions here have changed very little in the past century, and the people are not normally very mobile. Parts of the Sudan, in particular the Upper Nile region, are almost totally cut off from the rest of the country, and most people tend to remain at their place of birth.

Mosquito-borne diseases, such as dengue fever and malaria, typically affect third world countries and areas with tropical climates. Mosquito vectors are sensitive to climate changes and tend to follow seasonal patterns. Between years there are often dramatic shifts in incidence rates. The occurrence of this phenomenon in endemic areas makes mosquito-borne viruses difficult to treat.

Dengue fever is caused by infection through viruses of the family Flaviviridae. The illness is most commonly transmitted by Aedes aegypti mosquitoes in tropical and subtropical regions. Dengue virus has four different serotypes, each of which are antigenically related but have limited cross-immunity to reinfection.

Although dengue fever has a global incidence of 50-100 million cases, only several hundreds of thousands of these cases are life-threatening. The geographic prevalence of the disease can be examined by the spread of the Aedes aegypti. Over the last twenty years, there has been a geographic spread of the disease. Dengue incidence rates have risen sharply within urban areas which have recently become endemic hot spots for the disease. The recent spread of Dengue can also be attributed to rapid population growth, increased coagulation in urban areas, and global travel. Without sufficient vector control, the dengue virus has evolved rapidly over time, posing challenges to both government and public health officials.

Malaria is caused by a protozoan called Plasmodium falciparum. P. falciparum parasites are transmitted mainly by the Anopheles gambiae complex in rural Africa. In just this area, P. falciparum infections comprise an estimated 200 million clinical cases and 1 million annual deaths. 75% of individuals afflicted in this region are children. As with dengue, changing environmental conditions have led to novel disease characteristics. Due to increased illness severity, treatment complications, and mortality rates, many public health officials concede that malaria patterns are rapidly transforming in Africa. Scarcity of health services, rising instances of drug resistance, and changing vector migration patterns are factors that public health officials believe contribute to malaria’s dissemination.

Climate heavily affects mosquito vectors of malaria and dengue. Climate patterns influence the lifespan of mosquitos as well as the rate and frequency of reproduction. Climate change impacts have been of great interest to those studying these diseases and their vectors. Additionally, climate impacts mosquito blood feeding patterns as well as extrinsic incubation periods. Climate consistency gives researchers an ability to accurately predict annual cycling of the disease but recent climate unpredictability has eroded researchers’ ability to track the disease with such precision.

Globally, an estimated 125 million or more pregnant women per year risk contracting PAM. Pregnancy-related malaria causes around 100,000 infant deaths each year, due in large part to low birth weight.

There are no vaccines or preventive drugs for visceral leishmaniasis. The most effective method to prevent infection is to protect from sand fly bites. To decrease the risk of being bitten, these precautionary measures are suggested:

- Outdoors:

1. Avoid outdoor activities, especially from dusk to dawn, when sand flies generally are the most active.

2. When outdoors (or in unprotected quarters), minimize the amount of exposed (uncovered) skin to the extent that is tolerable in the climate. Wear long-sleeved shirts, long pants, and socks; and tuck your shirt into your pants.

3. Apply insect repellent to exposed skin and under the ends of sleeves and pant legs. Follow the instructions on the label of the repellent. The most effective repellents generally are those that contain the chemical DEET (N,N-diethylmetatoluamide).

- Indoors:

1. Stay in well-screened or air-conditioned areas.

2. Keep in mind that sand flies are much smaller than mosquitoes and therefore can get through smaller holes.

3. Spray living/sleeping areas with an insecticide to kill insects.

4. If you are not sleeping in a well-screened or air-conditioned area, use a bed net and tuck it under your mattress. If possible, use a bed net that has been soaked in or sprayed with a pyrethroid-containing insecticide. The same treatment can be applied to screens, curtains, sheets, and clothing (clothing should be retreated after five washings)."

On February 2012, the nonprofit Infectious Disease Research Institute launched a clinical trial of the visceral leishmaniasis vaccine. The vaccine is a recombinant form of two fused Leishmania parasite proteins with an adjuvant. Two phase 1 clinical trials with healthy volunteers are to be conducted. The first one takes place in Washington (state) and is followed by a trial in India.

The arboviruses have expanded their geographic range and infected populations that had no recent community knowledge of the diseases carried by the "Aedes aegypti" mosquito. Education and community awareness campaigns are necessary for prevention to be effective. Communities are educated on how the disease is spread, how they can protect themselves from infection and the symptoms of infection. Community health education programs can identify and address the social/economic and cultural issues that can hinder preventative measures. Community outreach and education programs can identify which preventative measures a community is most likely to employ. Leading to a targeted prevention method that has a higher chance of success in that particular community. Community outreach and education includes engaging community health workers and local healthcare providers, local schools and community organizations to educate the public on mosquito vector control and disease prevention.

More than 300 million people worldwide have asthma. The rate of asthma increases as countries become more urbanized and in many parts of the world those who develop asthma do not have access to medication and medical care. Within the United States, African Americans and Latinos are four times more likely to suffer from severe asthma than whites. The disease is closely tied to poverty and poor living conditions. Asthma is also prevalent in children in low income countries. Homes with roaches and mice, as well as mold and mildew put children at risk for developing asthma as well as exposure to cigarette smoke.

Unlike many other Western countries, the mortality rate for asthma has steadily risen in the United States over the last two decades. Mortality rates for African American children due to asthma are also far higher than that of other racial groups. For African Americans, the rate of visits to the emergency room is 330 percent higher than their white counterparts. The hospitalization rate is 220 percent higher and the death rate is 190 percent higher. Among Hispanics, Puerto Ricans are disporpotionatly affected by asthma with a disease rate that is 113 percent higher than non-Hispanic Whites and 50 percent higher than non-Hispanic Blacks. Studies have shown that asthma morbidity and mortality are concentrated in inner city neighborhoods characterized by poverty and large minority populations and this affects both genders at all ages. Asthma continues to have an adverse effects on the health of the poor and school attendance rates among poor children. 10.5 million days of school are missed each year due to asthma.

Though heart disease is not exclusive to the poor, there are aspects of a life of poverty that contribute to its development. This category includes coronary heart disease, stroke and heart attack. Heart disease is the leading cause of death worldwide and there are disparities of morbidity between the rich and poor. Studies from around the world link heart disease to poverty. Low neighborhood income and education were associated with higher risk factors. Poor diet, lack of exercise and limited (or no) access to a specialist were all factors related to poverty, though to contribute to heart disease.

Both low income and low education were predictors of coronary heart disease, a subset of cardiovascular disease. Of those admitted to hospital in the United States for heart failure, women and African Americans were more likely to reside in lower income neighborhoods. In the developing world, there is a 10 fold increase in cardiac events in the black and urban populations.

There is some debate among the WHO, CDC, and infectious disease experts over which diseases are classified as neglected tropical diseases. Feasey, a researcher in neglected tropical diseases, notes 13 neglected tropical diseases: ascariasis, Buruli ulcer, Chagas disease, dracunculiasis, hookworm infection, human African trypanosomiasis, Leishmaniasis, leprosy, lymphatic filariasis, onchocerciasis, schistosomiasis, trachoma, and trichuriasis. Fenwick recognizes 12 "core" neglected tropical diseases: ascariasis, Buruli ulcer, Chagas disease, dracunculiasis, human African trypanosomiasis, Leishmaniasis, leprosy, lymphatic filariasis, onchocerciasis, schistosomiasis, trachoma, and trichuriasis.

These diseases result from four different classes of causative pathogens: (i) protozoa (for Chagas disease, human African trypanosomiasis, leishmaniases); (ii) bacteria (for Buruli ulcer, leprosy, trachoma, yaws), (iii) helminths or metazoan worms (for cysticercosis/taeniasis, dracunculiasis, echinococcosis, foodborne trematodiases, lymphatic filariasis, onchocerciasis, schistosomiasis, soil-transmitted helminthiasis); and (iv) viruses (dengue and chikungunya, rabies).

The World Health Organization recognizes the seventeen diseases below as neglected tropical diseases.

The disease results from the aggregation of erythrocytes infected by "Plasmodium falciparum" which have been shown to adhere to chondroitin sulfate A (CSA) on placental proteoglycans causing them to accumulate in the intervillous spaces of the placenta, blocking the crucial flow of nutrients from mother to embryo.

About 15–20% of hospitalized Lassa fever patients will die from the illness. The overall mortality rate is estimated to be 1%, but during epidemics, mortality can climb as high as 50%. The mortality rate is greater than 80% when it occurs in pregnant women during their third trimester; fetal death also occurs in nearly all those cases. Abortion decreases the risk of death to the mother. Some survivors experience lasting effects of the disease, and can include partial or complete deafness.

Because of treatment with ribavirin, fatality rates are continuing to decline.

Deworming treatments in infected children may have some nutritional benefit, as worms are often partially responsible for malnutrition. However, in areas where these infections are common, there is strong evidence that mass deworming campaigns do not have a positive effect on children's average nutritional status, levels of blood haemoglobin, cognitive abilities, performance at school or survival. To achieve health gains in the longer term, improvements in sanitation and hygiene behaviours are also required, together with deworming treatments.

Additional neglected tropical diseases include:

Some tropical diseases are very rare, but may occur in sudden epidemics, such as the Ebola hemorrhagic fever, Lassa fever and the Marburg virus. There are hundreds of different tropical diseases which are less known or rarer, but that, nonetheless, have importance for public health.

Some of the strategies for controlling tropical diseases include:

- Draining wetlands to reduce populations of insects and other vectors, or introducing natural predators of the vectors.

- The application of insecticides and/or insect repellents) to strategic surfaces such as clothing, skin, buildings, insect habitats, and bed nets.

- The use of a mosquito net over a bed (also known as a "bed net") to reduce nighttime transmission, since certain species of tropical mosquitoes feed mainly at night.

- Use of water wells, and/or water filtration, water filters, or water treatment with water tablets to produce drinking water free of parasites.

- Sanitation to prevent transmission through human waste.

- In situations where vectors (such as mosquitoes) have become more numerous as a result of human activity, a careful investigation can provide clues: for example, open dumps can contain stagnant water that encourage disease vectors to breed. Eliminating these dumps can address the problem. An education campaign can yield significant benefits at low cost.

- Development and use of vaccines to promote disease immunity.

- Pharmacologic pre-exposure prophylaxis (to prevent disease before exposure to the environment and/or vector).

- Pharmacologic post-exposure prophylaxis (to prevent disease after exposure to the environment and/or vector).

- Pharmacologic treatment (to treat disease after infection or infestation).

- Assisting with economic development in endemic regions. For example, by providing microloans to enable investments in more efficient and productive agriculture. This in turn can help subsistence farming to become more profitable, and these profits can be used by local populations for disease prevention and treatment, with the added benefit of reducing the poverty rate.

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Treatment of asymptomatic carriers should be considered if parasites are still detected after 3 months. In mild-to-moderate babesiosis, the treatment of choice is a combination of atovaquone and azithromycin. This regimen is preferred to clindamycin and quinine because side effects are fewer. The standard course is 7 to 10 days, but this is extended to at least 6 weeks in people with relapsing disease. Even mild cases are recommended to be treated to decrease the chance of inadvertently transmitting the infection by donating blood. In life-threatening cases, exchange transfusion is performed. In this procedure, the infected red blood cells are removed and replaced with uninfected ones.

Imizol is a drug used for treatment of babesiosis in dogs.

Extracts of the poisonous, bulbous plant "Boophone disticha" are used in the folk medicine of South Africa to treat equine babesiosis. "B. disticha" is a member of the daffodil family Amaryllidaceae and has also been used in preparations employed as arrow poisons, hallucinogens, and in embalming. The plant is rich in alkaloids, some of which display an action similar to that of scopolamine.

For many years from the 1950s onwards, vast dams and irrigation schemes were constructed, causing a massive rise in water-borne infections from schistosomiasis. The detailed specifications laid out in various UN documents since the 1950s could have minimized this problem. Irrigation schemes can be designed to make it hard for the snails to colonize the water and to reduce the contact with the local population. Even though guidelines on how to design these schemes to minimise the spread of the disease had been published years before, the designers were unaware of them. The dams appear to have reduced the population of the large migratory prawn "Macrobrachium". After the construction of fourteen large dams, greater increases in schistosomiasis occurred in the historical habitats of native prawns than in other areas. Further, at the 1986 Diama Dam on the Senegal River, restoring prawns upstream of the dam reduced both snail density and the human schistosomiasis reinfection rate.

"Babesia" parasites reproduce in red blood cells, where they can be seen as cross-shaped inclusions (four merozoites asexually budding, but attached together forming a structure looking like a "Maltese cross") and cause hemolytic anemia, quite similar to malaria.

Unlike the "Plasmodium" parasites that cause malaria, "Babesia" species lack an exoerythrocytic phase, so the liver is usually not affected.

In nonhuman animals, "Babesia canis rossi", "Babesia bigemina", and "Babesia bovis" cause particularly severe forms of the disease, including a severe haemolytic anaemia, with positive erythrocyte-in-saline-agglutination test indicating an immune-mediated component to the haemolysis. Common sequelae include haemoglobinuria "red-water", disseminated intravascular coagulation, and "cerebral babesiosis" caused by sludging of erythrocytes in cerebral capillaries.

In bovine species, the organism causes hemolytic anemia, so an infected animal shows pale mucous membranes initially. As the levels of bilirubin (a byproduct of red blood cell lysis) continue to increase, the visible mucous membranes become yellow in color (icterus) due to the failure of the liver to metabolize the excess bilirubin. Hemoglobinuria is seen due to excretion of red-blood-cell lysis byproducts via the kidneys. Fever of 40.5 °C (105 °F) develops due to release of inflammatory byproducts.

The disease is found in tropical countries in Africa, the Caribbean, eastern South America, Southeast Asia, and the Middle East. "S. mansoni" is found in parts of South America and the Caribbean, Africa, and the Middle East; "S. haematobium" in Africa and the Middle East; and "S. japonicum" in the Far East. "S. mekongi" and "S. intercalatum" are found locally in Southeast Asia and central West Africa, respectively.

The disease is endemic in about 75 developing countries and mainly affects people living in rural agricultural and peri-urban areas.

In 2012, the World Health Organization estimated that vaccination prevents 2.5 million deaths each year. If there is 100% immunization, and 100% efficacy of the vaccines, one out of seven deaths among young children could be prevented, mostly in developing countries, making this an important global health issue. Four diseases were responsible for 98% of vaccine-preventable deaths: measles, "Haemophilus influenzae" serotype b, pertussis, and neonatal tetanus.

The Immunization Surveillance, Assessment and Monitoring program of the WHO monitors and assesses the safety and effectiveness of programs and vaccines at reducing illness and deaths from diseases that could be prevented by vaccines.

Vaccine-preventable deaths are usually caused by a failure to obtain the vaccine in a timely manner. This may be due to financial constraints or to lack of access to the vaccine. A vaccine that is generally recommended may be medically inappropriate for a small number of people due to severe allergies or a damaged immune system. In addition, a vaccine against a given disease may not be recommended for general use in a given country, or may be recommended only to certain populations, such as young children or older adults. Every country makes its own vaccination recommendations, based on the diseases that are common in its area and its healthcare priorities. If a vaccine-preventable disease is uncommon in a country, then residents of that country are unlikely to receive a vaccine against it. For example, residents of Canada and the United States do not routinely receive vaccines against yellow fever, which leaves them vulnerable to infection if travelling to areas where risk of yellow fever is highest (endemic or transitional regions).

The Lassa virus commonly spreads to humans from other animals, specifically a rodent known as a natal multimammate mouse ("Mastomys natalensis"). This is probably the most common mouse in equatorial Africa, common in human households and eaten as a delicacy in some areas. It is also called the "natal multimammate rat" or African rat.

The Multimammate rat can quickly produce a large number of offspring, tends to colonize human settlements increasing the risk of rodent-human contact, and is found throughout the west, central and eastern parts of the African continent. Once the rat has become a carrier, it will excrete the virus throughout the rest of its lifetime through feces and urine creating ample opportunity for exposure. The virus is probably transmitted by contact with the feces or urine of animals accessing grain stores in residences.

Infection in humans typically occurs by direct or indirect exposure to animal excrement through the respiratory or gastrointestinal tracts. Inhalation of tiny particles of infectious material (aerosol) is believed to be the most significant means of exposure. It is possible to acquire the infection through broken skin or mucous membranes that are directly exposed to infectious material. Transmission from person to person has also been established, presenting a disease risk for healthcare workers in the clinical setting. The virus is still present in the urine for between three and nine weeks after infection, and it can be transmitted in semen for up to three months after becoming infected. Individuals who are at a higher risk of contracting the infection are those who live in rural areas where Mastromys are discovered, more specifically in socioeconomic societies where sanitation isn't prevalent.

The cause of hemolytic crises in this disease is unknown (mainly due to intravascular haemolysis). There is rapid and massive destruction of red blood cells resulting in hemoglobinemia (hemoglobin in the blood, but outside the red blood cells), hemoglobinuria (hemoglobin in urine), intense jaundice, anuria (passing less than 50 milliliters of urine in a day), and finally death in the majority of cases.

The most probable explanation for blackwater fever is an autoimmune reaction apparently caused by the interaction of the malaria parasite and the use of quinine. Blackwater fever is caused by heavy parasitization of red blood cells with "Plasmodium falciparum". There has been at least one case, however, attributed to "Plasmodium vivax".

Blackwater fever is a serious complication of malaria, but cerebral malaria has a higher mortality rate. Blackwater fever is much less common today than it was before 1950. It may be that quinine plays a role in triggering the condition, and this drug is no longer commonly used for malaria prophylaxis. Quinine remains important for treatment of malaria.

A "vaccine-preventable disease" is an infectious disease for which an effective preventive vaccine exists. If a person acquires a vaccine-preventable disease and dies from it, the death is considered a vaccine-preventable death.

The most common and serious vaccine-preventable diseases tracked by the World Health Organization (WHO) are: diphtheria, "Haemophilus influenzae" serotype b infection, hepatitis B, measles, meningitis, mumps, pertussis, poliomyelitis, rubella, tetanus, tuberculosis, and yellow fever. The WHO reports licensed vaccines being available to prevent, or contribute to the prevention and control of, 25 vaccine-preventable infections.

Tropical and sub-tropical regions are the main areas affected by nematodes and parasitic worms, which often causes filariasis. Around 20% of immigrants to Spain are children from these regions. There are concerns about absolute eosinophilia in immigrants that is correlated with parasitic diseases that may go undiagnosed. Absolute eosinophilia is clinically diagnosed as >0.45×10 eosinophilic leucocytes/L of peripheral blood. Recent studies suggest that around 60% of children with relative eosinophilia contracted this via parasitic infections. Relative eosinophilia is different from absolute because relative refers to an increase in percentage of white blood cells (i.e. leukocytes) due to a loss of blood plasma; where as absolute eosinophilia is purely an increase in white blood cell production. Of those with relative eosinophilia, 40% were undiagnosed until these studies. Therefore, there is a great need for thorough parasitological studies in this area of tropical infectious diseases.

The treatment is antimalarial chemotherapy, intravenous fluid and sometimes supportive care such as intensive care and dialysis.