Health is the valuable asset for human.We can not happy without good health.All animals need good health for live.But sometimes we are face many dangerous diseases.Diseases is harmful for all animal.If we can't know about diseases harmful after we suffer by this diseases.As a result we should knowing about diseases.Some common diseases short description analyses below:
Avian influenza A (H5N1) virus
The Ministry of Health and Population of Egypt has notified WHO of a new case of human infection with avian influenza A (H5N1) virus.
The case is a 45 year-old female from Menofia governorate. She developed symptoms on 10 February 2012, received oseltamivir treatment on 17 February 2012 and is still recovering. The case was laboratory confirmed by the Central Public Health Laboratories; a National Influenza Center of the WHO Global Influenza Surveillance Network on 18 February 2012.
Epidemiological investigation into the source of infection indicate that the case had exposure to backyard poultry.
Of the 160 cases confirmed to date in Egypt, 55 have been fatal.
Anthrax
Anthrax is primarily a disease of herbivorous mammals, although other mammals and some birds have been known to contract it. Until the introduction and widespread use of effective veterinary vaccines, it was a major cause of fatal disease in cattle, sheep, goats, camels, horses, and pigs throughout the world. Anthrax continues to be reported from many countries in domesticated and wild herbivores, especially where livestock vaccination programmes are inadequate or have been disrupted.
Humans generally acquire the disease directly or indirectly from infected animals, or occupational exposure to infected or contaminated animal products. Control in livestock is therefore the key to reduced incidence. The disease is generally regarded as being non-contagious. Records of person-to-person spread exist, but are rare.
Influenza viruses circulating in animals pose threats to human health. Humans can become ill when infected with viruses from animal sources, such as avian influenza virus subtypes H5N1 and H9N2 and swine influenza virus subtypes H1N1 and H3N2. The primary risk factor for human infection appears to be direct or indirect exposure to infected live or dead animals or contaminated
environments.
Crimean-Congo Hemorrhagic fever is a viral haemorrhagic fever transmitted by ticks. It can be responsible for severe outbreaks in humans but it is not pathogenic for ruminants, their amplifying host.
The disease was first described in the Crimea in 1944 and given the name Crimean haemorrhagic fever. In 1969 it was recognized that the pathogen causing Crimean haemorrhagic fever was the same as that responsible for an illness identified in 1956 in the Congo, and linkage of the two place names resulted in the current name for the disease and the virus.
CCHF spreads to humans either by tick-bites, or through contact with viraemic animal tissues during and immediately post-slaughter. CCHF outbreaks constitute a threat to public health services because of its epidemic potential, its high case fatality ratio (10-40%), its potential for nosocomial outbreaks and the difficulties in treatment and prevention. CCHF is endemic in all of Africa, the Balkans, the Middle East and in Asia south of the 50° parallel north, the geographic limit of the genus Hyalomma, the principal tick vector.
Ebola haemorrhagic fever (EHF) is a viral haemorrhagic fever and one of the most virulent viral diseases known to humankind.
The Ebola virus was first identified in the western equatorial province of Sudan and in a nearby region of Zaire (now Democratic Republic of the Congo) in 1976 after significant epidemics in Nzara, southern Sudan and Yambuku, northern Zaire.
There are five distinct species of the Ebola virus: Bundibugyo, Côte d’Ivoire, Reston, Sudan and Zaïre. Bundibugyo, Sudan and Zaïre species have been associated with large outbreaks of Ebola haemorrhagic fever (EHF) in Africa causing death in 25-90% of all clinically ill cases, while Côte d’Ivoire and Reston have not.
The Ebola virus is transmitted by direct contact with the blood, body fluids and tissues of infected persons. Transmission of the Ebola virus has also occurred by handling sick or dead infected wild animals (chimpanzees, gorillas, monkeys, forest antelope, fruit bats). The predominant treatment is general supportive therapy.
Hendra virus (HeV) infection is a rare emerging zoonosis that causes severe disease in both infected horses and humans. The natural host of the virus has been identified as being fruit bats of the Pteropodidae Family, Pteropus genus.
HeV was first identified during the first recorded outbreak of the disease that took place in the Brisbane suburb of Hendra, Australia, in 1994. The outbreak involved 21 horses and two human cases. As of July 2008, eleven outbreaks have been reported, all confined to the east cost of Australia. Horses have been identified as the intermediate hosts, transmitting infection to humans through close contact during care or necropsy of the ill or dead horses.
Symptoms of HeV infection in humans range from mild influenza-like illness to fatal respiratory or neurological disease. Horses are the only animal species in which natural infection of HeV has been reported, with a case fatality of approximately 75%. There is no vaccine for either humans or animals. The primary treatment for human cases is intensive supportive care.
Hepatitis is an inflammation of the liver, most commonly caused by a viral infection. There are five main hepatitis viruses, referred to as types A, B, C, D and E. These five types are of greatest concern because of the burden of illness and death they cause and the potential for outbreaks and epidemic spread. In particular, types B and C lead to chronic disease in hundreds of millions of people and, together, are the most common cause of liver cirrhosis and cancer.
Hepatitis A and E are typically caused by ingestion of contaminated food or water. Hepatitis B, C and D usually occur as a result of parenteral contact with infected body fluids. Common modes of transmission for these viruses include receipt of contaminated blood or blood products, invasive medical procedures using contaminated equipment and for hepatitis B transmission from mother to baby at birth, from family member to child, and also by sexual contact.
Acute infection may occur with limited or no symptoms, or may include symptoms such as jaundice (yellowing of the skin and eyes), dark urine, extreme fatigue, nausea, vomiting and abdominal pain.
Human Monkeypox (MPX)
Monkeypox virus (MPXV) is an orthopoxvirus that causes human monkeypox (MPX), a viral disease with symptoms in humans similar to that seen in smallpox patients. Smallpox no longer occurs, following its worldwide eradication in 1980, whereas human monkeypox is regularly reported in villages of Central and West Africa close to tropical rainforest where there is frequent contact with infected animals.
Monkeypox is usually transmitted to humans from non-human primates, squirrels or other rodents (e.g. Gambian rats) through contact with the infected animal’s blood or through a bite. Humans also acquire the disease through direct contact with infected patients but there is no evidence to date that person-to-person transmission alone can sustain MPX in the human population.
In November 2005, several MPX cases were reported in Bentiu, Unity State, Sudan. This was the first time MPX has been reported in a dry savannah environment in Africa.
Smallpox
Smallpox is an acute contagious disease caused by Variola virus, a member of the orthopoxvirus family. It was one of the world's most feared diseases until it was eradicated by a collaborative global vaccination programme led by the World Health Organization. The last known natural case was in Somalia in 1977. Since then, the only known cases were caused by a laboratory accident in 1978 in Birmingham, England, which killed one person and caused a limited outbreak. Smallpox was officially declared eradicated in 1979.
Tularaemia is primarily a disease of a wide variety of wild mammals and birds. Humans become infected mainly through the bite of arthropods, particularly ticks and mosquitoes, and through the skin, conjunctival sac or oropharyngeal mucosa, by direct contact with infected animals or animal materials and by ingestion of contaminated food or water or inhalation of contaminated dust or aerosols.
F. tularensis is easily transmitted by aerosols and inhalation of only a few organisms is likely to cause infection. Person-to-person transmission has not been documented.
Meningococcal disease, also referred to as cerebrospinal meningitis is a contagious bacterial disease caused by the meningococcus (Neisseria meningitidis). It is spread by person-to-person contact through respiratory droplets of infected people. There are 3 main clinical forms of the disease: the meningeal syndrome, the septic form and pneumonia. The onset of symptoms is sudden and death can follow within hours. In as many as 10-15% of survivors, there are persistent neurological defects, including hearing loss, speech disorders, loss of limbs, mental retardation and paralysis.
N. meningitidis inhabits the mucosal membrane of the nose and throat, where it usually causes no harm. Up to 5-10% of a population may be asymptomatic carriers. These carriers are crucial to the spread of the disease as most cases are acquired through exposure to asymptomatic carriers. Waning immunity among the population against a particular strain favours epidemics, as do overcrowding and climatic conditions such as dry seasons or prolonged drought and dust storms. Smoking, mucosal lesions and concomitant respiratory infections are considered risk factors that may contribute to the development of the disease. The disease mainly affects young children, but is also common in older children and young adults.
The disease occurs sporadically throughout the world with seasonal variations and accounts for a proportion of endemic bacterial meningitis. However, the highest burden of the disease is due to the cyclic epidemics occurring in the African meningitis belt.
Lassa fever
Lassa fever is an acute viral haemorrhagic illness caused by Lassa virus, a member of the arenavirus family of viruses. It is transmitted to humans from contacts with food or household items contaminated with rodent excreta. The disease is endemic in the rodent population in parts of West Africa. Person-to-person infections and laboratory transmission can also occur, particularly in the hospital environment in the absence of adequate infection control measures. Diagnosis and prompt treatment are essential.
Marburg haemorrhagic fever
Marburg haemorrhagic fever (MHF) was first identified in 1967 during epidemics in Marburg and Frankfurt in Germany and Belgrade in the former Yugoslavia from importation of infected monkeys from Uganda. MHF is a viral haemorrhagic fever and a severe and highly fatal disease caused by a virus from the same family as the one that causes Ebola haemorrhagic fever. These viruses are among the most virulent pathogens known to infect humans. Both diseases are rare, but have a capacity to cause dramatic outbreaks with high fatality.
Illness caused by Marburg virus begins abruptly, with severe headache and severe malaise. Many patients develop severe haemorrhagic manifestations between days 5 and 7, and fatal cases usually have some form of bleeding, often from multiple sites. The disease has no vaccine and no specific treatment. Case fatality rates have varied greatly, from 25% in the initial laboratory-associated outbreak in 1967, to more than 80% in the Democratic Republic of Congo from 1998-2000, to even higher in the outbreak that began in Angola in late 2004.
The Marburg virus is transmitted by direct contact with the blood, body fluids and tissues of infected persons. Transmission of the Marburg virus also occurred by handling ill or dead infected wild animals (monkeys, fruit bats). The predominant treatment is general supportive therapy.
Nipah virus (NiV) infection is a newly emerging zoonosis that causes severe disease in both animals and humans. The natural host of the virus are fruit bats of the Pteropodidae Family, Pteropus genus.
NiV was first identified during an outbreak of disease that took place in Kampung Sungai Nipah, Malaysia in 1998. On this occasion, pigs were the intermediate hosts. However, in subsequent NiV outbreaks, there were no intermediate hosts. In Bangladesh in 2004, humans became infected with NiV as a result of consuming date palm sap that had been contaminated by infected fruit bats. Human-to-human transmission has also been documented, including in a hospital setting in India.
NiV infection in humans has a range of clinical presentations, from asymptomatic infection to acute respiratory syndrome and fatal encephalitis. NiV is also capable of causing disease in pigs and other domestic animals. There is no vaccine for either humans or animals. The primary treatment for human cases is intensive supportive care.
One of the oldest identifiable diseases known to man, plague remains endemic in many natural foci around the world. It is still widely distributed in the tropics and subtropics and in warmer areas of temperate countries. Essentially a disease of wild rodents, plague is spread from one rodent to another by flea ectoparasites and to humans either by the bite of infected fleas or when handling infected hosts. Recent outbreaks have shown that plague may reoccur in areas that have long remained silent.
Untreated, mortality - particularly from pneumonic plague - may reach high levels. When rapidly diagnosed and promptly treated, plague may be successfully managed with antibiotics such as streptomycin and tetracycline, reducing mortality from 60% to less than 15%.
Rift Valley fever (RVF) is a viral zoonosis that was first identified in Kenya in 1931. This mosquito-borne disease primarily affects animals but that also has the capacity to infect humans. The vast majority of human infections result from direct or indirect contact with the blood or organs of infected animals. Such contact may occur during the care or slaughtering of infected animals or possibly from the ingestion of raw milk. Human infection can also result from the bites of infected mosquitoes.
While most human cases are relatively mild, a small percentage of patients develop a much more severe form of the disease that appears as one or more of three distinct syndromes: ocular disease, meningoencephalitis and viral haemorrhagic fever. For the most severs cases, the predominant treatment is general supportive therapy.
RVF outbreaks in East Africa are closely associated with periods of heavy rainfall that occurs during the warm phase of the El Niño/Southern Oscillation (ENSO) phenomenon. These findings have enabled the successful development of forecasting models and early warning systems for RVF using satellite images and weather/climate forecasting data enabling authorities to implement measures to avert impending epidemics.
Yellow fever (YF) is a viral haemorrhagic fever transmitted by infected mosquitoes.
Yellow fever can be recognized from historic texts stretching back 400 years. Infection causes a wide spectrum of disease, from mild symptoms to severe illness and death. The "yellow" in the name is explained by the jaundice that affects some patients, causing yellow eyes and yellow skin.
There are three types of transmission cycle: sylvatic, intermediate and urban. All three cycles exist in Africa, but in South America, only sylvatic and urban yellow fever occur.Sylvatic (or jungle) yellow fever occurs in tropical rainforests where monkeys, infected by sylvatic mosquitoes, pass the virus onto other mosquitoes that feed on them; these mosquitoes, in turn bite and infect humans entering the forest. This produces sporadic cases, the majority of which are often young men working in the forest e.g. logging.
The intermediate cycle of yellow fever transmission occurs in humid or semi-humid savannahs of Africa, and can produce small-scale epidemics in rural villages. Semi-domestic mosquitoes infect both monkey and human hosts and increased contact between man and infected mosquito leads to disease. This is the most common type of outbreak seen in recent decades in Africa.
Urban yellow fever results in large explosive epidemics when travellers from rural areas introduce the virus into areas with high human population density. Domestic mosquitoes, most notably Aedes aegypti, carry the virus from person to person. These outbreaks tend to spread outwards from one source to cover a wide area.
Yellow fever can be prevented by vaccination. In order to protect people living in areas at high risk of yellow fever transmission, WHO's dual strategy for prevention of yellow fever epidemics relies on preventive mass immunization campaigns followed by infant routine immunization.
Yellow fever causes epidemics that can affect 20% of the population. When epidemics occur in unvaccinated populations, case-fatality rates may exceed 50%. No treatment beyond supportive care exists.
Dengue/dengue haemorrhagic fever
Dengue is the most common mosquito-borne viral disease of humans that in recent years has become a major international public health concern. Globally, 2.5 billion people live in areas where dengue viruses can be transmitted. The geographical spread of both the mosquito vectors and the viruses has led to the global resurgence of epidemic dengue fever and emergence of dengue hemorrhagic fever (dengue/DHF) in the past 25 years with the development of hyperendemicity in many urban centers of the tropics.
Transmitted by the main vector, the Aedes aegytpi mosquito, there are four distinct, but closely related, viruses that cause dengue. Recovery from infection by one provides lifelong immunity against that serotype but confers only partial and transient protection against subsequent infection by the other three. There is good evidence that sequential infection increases the risk of more serious disease resulting in DHF.
DHF was first recognized in the 1950s during the dengue epidemics in the Philippines and Thailand. By 1970 nine countries had experienced epidemic DHF and now, the number has increased more than fourfold and continues to rise. Today emerging DHF cases are causing increased dengue epidemics in the Americas, and in Asia, where all four dengue viruses are endemic, DHF has become a leading cause of hospitalization and death among children in several countries.
Currently vector control is the available method for the dengue and DHF prevention and control but research on dengue vaccines for public health use is in process. The global strategy for dengue /DHF prevention and control developed by WHO and the regional strategy formulation in the Americas, South-East Asia and the Western Pacific during the 1990s have facilitated identification of the main priorities: strengthening epidemiological surveillance through the implementation of DengueNet; accelerated training and the adoption of WHO standard clinical management guidelines for DHF; promoting behavioral change at individual, household and community levels to improve prevention and control; and accelerating research on vaccine development, host-pathogen interactions, and development of tools/interventions by including dengue in the disease portfolio of TDR (UNDP/World Bank/WHO Special Programme for Research and Training in Tropical Diseases) and IVR (WHO Initiative for Vaccine Research)
Avian influenza A (H5N1) virus
The Ministry of Health and Population of Egypt has notified WHO of a new case of human infection with avian influenza A (H5N1) virus.
The case is a 45 year-old female from Menofia governorate. She developed symptoms on 10 February 2012, received oseltamivir treatment on 17 February 2012 and is still recovering. The case was laboratory confirmed by the Central Public Health Laboratories; a National Influenza Center of the WHO Global Influenza Surveillance Network on 18 February 2012.
Epidemiological investigation into the source of infection indicate that the case had exposure to backyard poultry.
Of the 160 cases confirmed to date in Egypt, 55 have been fatal.
Anthrax
Humans generally acquire the disease directly or indirectly from infected animals, or occupational exposure to infected or contaminated animal products. Control in livestock is therefore the key to reduced incidence. The disease is generally regarded as being non-contagious. Records of person-to-person spread exist, but are rare.
Avian influenza
environments.
Crimean-Congo haemorrhagic fever (CCHF)
The disease was first described in the Crimea in 1944 and given the name Crimean haemorrhagic fever. In 1969 it was recognized that the pathogen causing Crimean haemorrhagic fever was the same as that responsible for an illness identified in 1956 in the Congo, and linkage of the two place names resulted in the current name for the disease and the virus.
CCHF spreads to humans either by tick-bites, or through contact with viraemic animal tissues during and immediately post-slaughter. CCHF outbreaks constitute a threat to public health services because of its epidemic potential, its high case fatality ratio (10-40%), its potential for nosocomial outbreaks and the difficulties in treatment and prevention. CCHF is endemic in all of Africa, the Balkans, the Middle East and in Asia south of the 50° parallel north, the geographic limit of the genus Hyalomma, the principal tick vector.
Ebola haemorrhagic fever
The Ebola virus was first identified in the western equatorial province of Sudan and in a nearby region of Zaire (now Democratic Republic of the Congo) in 1976 after significant epidemics in Nzara, southern Sudan and Yambuku, northern Zaire.
There are five distinct species of the Ebola virus: Bundibugyo, Côte d’Ivoire, Reston, Sudan and Zaïre. Bundibugyo, Sudan and Zaïre species have been associated with large outbreaks of Ebola haemorrhagic fever (EHF) in Africa causing death in 25-90% of all clinically ill cases, while Côte d’Ivoire and Reston have not.
The Ebola virus is transmitted by direct contact with the blood, body fluids and tissues of infected persons. Transmission of the Ebola virus has also occurred by handling sick or dead infected wild animals (chimpanzees, gorillas, monkeys, forest antelope, fruit bats). The predominant treatment is general supportive therapy.
Hendra Virus (HeV) Infection
HeV was first identified during the first recorded outbreak of the disease that took place in the Brisbane suburb of Hendra, Australia, in 1994. The outbreak involved 21 horses and two human cases. As of July 2008, eleven outbreaks have been reported, all confined to the east cost of Australia. Horses have been identified as the intermediate hosts, transmitting infection to humans through close contact during care or necropsy of the ill or dead horses.
Symptoms of HeV infection in humans range from mild influenza-like illness to fatal respiratory or neurological disease. Horses are the only animal species in which natural infection of HeV has been reported, with a case fatality of approximately 75%. There is no vaccine for either humans or animals. The primary treatment for human cases is intensive supportive care.
Hepatitis
Hepatitis A and E are typically caused by ingestion of contaminated food or water. Hepatitis B, C and D usually occur as a result of parenteral contact with infected body fluids. Common modes of transmission for these viruses include receipt of contaminated blood or blood products, invasive medical procedures using contaminated equipment and for hepatitis B transmission from mother to baby at birth, from family member to child, and also by sexual contact.
Acute infection may occur with limited or no symptoms, or may include symptoms such as jaundice (yellowing of the skin and eyes), dark urine, extreme fatigue, nausea, vomiting and abdominal pain.
Human Monkeypox (MPX)
Monkeypox virus (MPXV) is an orthopoxvirus that causes human monkeypox (MPX), a viral disease with symptoms in humans similar to that seen in smallpox patients. Smallpox no longer occurs, following its worldwide eradication in 1980, whereas human monkeypox is regularly reported in villages of Central and West Africa close to tropical rainforest where there is frequent contact with infected animals.
Monkeypox is usually transmitted to humans from non-human primates, squirrels or other rodents (e.g. Gambian rats) through contact with the infected animal’s blood or through a bite. Humans also acquire the disease through direct contact with infected patients but there is no evidence to date that person-to-person transmission alone can sustain MPX in the human population.
In November 2005, several MPX cases were reported in Bentiu, Unity State, Sudan. This was the first time MPX has been reported in a dry savannah environment in Africa.
Smallpox
Smallpox is an acute contagious disease caused by Variola virus, a member of the orthopoxvirus family. It was one of the world's most feared diseases until it was eradicated by a collaborative global vaccination programme led by the World Health Organization. The last known natural case was in Somalia in 1977. Since then, the only known cases were caused by a laboratory accident in 1978 in Birmingham, England, which killed one person and caused a limited outbreak. Smallpox was officially declared eradicated in 1979.
Tularaemia
Tularaemia is primarily a disease of a wide variety of wild mammals and birds. Humans become infected mainly through the bite of arthropods, particularly ticks and mosquitoes, and through the skin, conjunctival sac or oropharyngeal mucosa, by direct contact with infected animals or animal materials and by ingestion of contaminated food or water or inhalation of contaminated dust or aerosols.
F. tularensis is easily transmitted by aerosols and inhalation of only a few organisms is likely to cause infection. Person-to-person transmission has not been documented.
Meningococcal disease
Meningococcal disease, also referred to as cerebrospinal meningitis is a contagious bacterial disease caused by the meningococcus (Neisseria meningitidis). It is spread by person-to-person contact through respiratory droplets of infected people. There are 3 main clinical forms of the disease: the meningeal syndrome, the septic form and pneumonia. The onset of symptoms is sudden and death can follow within hours. In as many as 10-15% of survivors, there are persistent neurological defects, including hearing loss, speech disorders, loss of limbs, mental retardation and paralysis.
N. meningitidis inhabits the mucosal membrane of the nose and throat, where it usually causes no harm. Up to 5-10% of a population may be asymptomatic carriers. These carriers are crucial to the spread of the disease as most cases are acquired through exposure to asymptomatic carriers. Waning immunity among the population against a particular strain favours epidemics, as do overcrowding and climatic conditions such as dry seasons or prolonged drought and dust storms. Smoking, mucosal lesions and concomitant respiratory infections are considered risk factors that may contribute to the development of the disease. The disease mainly affects young children, but is also common in older children and young adults.
The disease occurs sporadically throughout the world with seasonal variations and accounts for a proportion of endemic bacterial meningitis. However, the highest burden of the disease is due to the cyclic epidemics occurring in the African meningitis belt.
Lassa fever
Lassa fever is an acute viral haemorrhagic illness caused by Lassa virus, a member of the arenavirus family of viruses. It is transmitted to humans from contacts with food or household items contaminated with rodent excreta. The disease is endemic in the rodent population in parts of West Africa. Person-to-person infections and laboratory transmission can also occur, particularly in the hospital environment in the absence of adequate infection control measures. Diagnosis and prompt treatment are essential.
Marburg haemorrhagic fever
Illness caused by Marburg virus begins abruptly, with severe headache and severe malaise. Many patients develop severe haemorrhagic manifestations between days 5 and 7, and fatal cases usually have some form of bleeding, often from multiple sites. The disease has no vaccine and no specific treatment. Case fatality rates have varied greatly, from 25% in the initial laboratory-associated outbreak in 1967, to more than 80% in the Democratic Republic of Congo from 1998-2000, to even higher in the outbreak that began in Angola in late 2004.
The Marburg virus is transmitted by direct contact with the blood, body fluids and tissues of infected persons. Transmission of the Marburg virus also occurred by handling ill or dead infected wild animals (monkeys, fruit bats). The predominant treatment is general supportive therapy.
Nipah Virus (NiV) Infection
NiV was first identified during an outbreak of disease that took place in Kampung Sungai Nipah, Malaysia in 1998. On this occasion, pigs were the intermediate hosts. However, in subsequent NiV outbreaks, there were no intermediate hosts. In Bangladesh in 2004, humans became infected with NiV as a result of consuming date palm sap that had been contaminated by infected fruit bats. Human-to-human transmission has also been documented, including in a hospital setting in India.
NiV infection in humans has a range of clinical presentations, from asymptomatic infection to acute respiratory syndrome and fatal encephalitis. NiV is also capable of causing disease in pigs and other domestic animals. There is no vaccine for either humans or animals. The primary treatment for human cases is intensive supportive care.
Plague
One of the oldest identifiable diseases known to man, plague remains endemic in many natural foci around the world. It is still widely distributed in the tropics and subtropics and in warmer areas of temperate countries. Essentially a disease of wild rodents, plague is spread from one rodent to another by flea ectoparasites and to humans either by the bite of infected fleas or when handling infected hosts. Recent outbreaks have shown that plague may reoccur in areas that have long remained silent.
Untreated, mortality - particularly from pneumonic plague - may reach high levels. When rapidly diagnosed and promptly treated, plague may be successfully managed with antibiotics such as streptomycin and tetracycline, reducing mortality from 60% to less than 15%.
Rift Valley fever
While most human cases are relatively mild, a small percentage of patients develop a much more severe form of the disease that appears as one or more of three distinct syndromes: ocular disease, meningoencephalitis and viral haemorrhagic fever. For the most severs cases, the predominant treatment is general supportive therapy.
RVF outbreaks in East Africa are closely associated with periods of heavy rainfall that occurs during the warm phase of the El Niño/Southern Oscillation (ENSO) phenomenon. These findings have enabled the successful development of forecasting models and early warning systems for RVF using satellite images and weather/climate forecasting data enabling authorities to implement measures to avert impending epidemics.
Yellow fever
Yellow fever can be recognized from historic texts stretching back 400 years. Infection causes a wide spectrum of disease, from mild symptoms to severe illness and death. The "yellow" in the name is explained by the jaundice that affects some patients, causing yellow eyes and yellow skin.
There are three types of transmission cycle: sylvatic, intermediate and urban. All three cycles exist in Africa, but in South America, only sylvatic and urban yellow fever occur.Sylvatic (or jungle) yellow fever occurs in tropical rainforests where monkeys, infected by sylvatic mosquitoes, pass the virus onto other mosquitoes that feed on them; these mosquitoes, in turn bite and infect humans entering the forest. This produces sporadic cases, the majority of which are often young men working in the forest e.g. logging.
The intermediate cycle of yellow fever transmission occurs in humid or semi-humid savannahs of Africa, and can produce small-scale epidemics in rural villages. Semi-domestic mosquitoes infect both monkey and human hosts and increased contact between man and infected mosquito leads to disease. This is the most common type of outbreak seen in recent decades in Africa.
Urban yellow fever results in large explosive epidemics when travellers from rural areas introduce the virus into areas with high human population density. Domestic mosquitoes, most notably Aedes aegypti, carry the virus from person to person. These outbreaks tend to spread outwards from one source to cover a wide area.
Yellow fever can be prevented by vaccination. In order to protect people living in areas at high risk of yellow fever transmission, WHO's dual strategy for prevention of yellow fever epidemics relies on preventive mass immunization campaigns followed by infant routine immunization.
Yellow fever causes epidemics that can affect 20% of the population. When epidemics occur in unvaccinated populations, case-fatality rates may exceed 50%. No treatment beyond supportive care exists.
Dengue/dengue haemorrhagic fever
Dengue is the most common mosquito-borne viral disease of humans that in recent years has become a major international public health concern. Globally, 2.5 billion people live in areas where dengue viruses can be transmitted. The geographical spread of both the mosquito vectors and the viruses has led to the global resurgence of epidemic dengue fever and emergence of dengue hemorrhagic fever (dengue/DHF) in the past 25 years with the development of hyperendemicity in many urban centers of the tropics.
Transmitted by the main vector, the Aedes aegytpi mosquito, there are four distinct, but closely related, viruses that cause dengue. Recovery from infection by one provides lifelong immunity against that serotype but confers only partial and transient protection against subsequent infection by the other three. There is good evidence that sequential infection increases the risk of more serious disease resulting in DHF.
DHF was first recognized in the 1950s during the dengue epidemics in the Philippines and Thailand. By 1970 nine countries had experienced epidemic DHF and now, the number has increased more than fourfold and continues to rise. Today emerging DHF cases are causing increased dengue epidemics in the Americas, and in Asia, where all four dengue viruses are endemic, DHF has become a leading cause of hospitalization and death among children in several countries.
Currently vector control is the available method for the dengue and DHF prevention and control but research on dengue vaccines for public health use is in process. The global strategy for dengue /DHF prevention and control developed by WHO and the regional strategy formulation in the Americas, South-East Asia and the Western Pacific during the 1990s have facilitated identification of the main priorities: strengthening epidemiological surveillance through the implementation of DengueNet; accelerated training and the adoption of WHO standard clinical management guidelines for DHF; promoting behavioral change at individual, household and community levels to improve prevention and control; and accelerating research on vaccine development, host-pathogen interactions, and development of tools/interventions by including dengue in the disease portfolio of TDR (UNDP/World Bank/WHO Special Programme for Research and Training in Tropical Diseases) and IVR (WHO Initiative for Vaccine Research)
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