Pandemic & Other Plagues of the 21st Century...
3 patterns of 21st century diseases: 12 diseases that altered human history
(1) Emerging (2) Zoonotic Diseases & (3) Nosocomial Infections.
Infectious diseases whose
humans has increased in the past 2 decades or threatens
The "miracle" antibiotics of the 1930's - 1950's seemed to eradicate most disease - cholera, thyphoid fever, diptheria, TB, malaria, and scores of other infections. But now we are again challenged by these recurring diseases, as well as newly emergent ones - AIDS, SARS, Lyme disease, West Nile virus, Hantavirus, Ebola, and by the reemergence of cholera, yellow fever, dengue fever.
Most emerging diseases are caused by changes in "microbial traffic"--that is, the introduction of existing pathogens into human populations from other species or their further dissemination from smaller to larger populations. This process is often precipitated by ecological or environmental changes and is facilitated by population movements and other social factors. Major influences include human demographics and behavior, technology and industry, economic development and land use, international travel and commerce, and breakdowns in public health measures.
environmental change (natural or manmade,
including weather changes, deforestation, earthquakes, etc...) affecting any
segment of the natural cycle might lead to the
emergence or reemergence of infectious diseases. Such events
can especially affect a class of diseases referred to as
in which a part of the
life cycle of the infectious agent is typically carried out in an arthropod
(e.g., mosquitoes and ticks) or mollusk, such as freshwater snails. The
role of the vector is to amplify and transmit the infectious agent.
After a century-long absence,
reappeared in the Western Hemisphere in 1991. Drastic population increases in
many Latin American countries made them susceptible to outbreaks of the bacteria
cholerae. The reappearance of plague,
cholera, and dengue
fever in many parts of the world is due in part to the rapid growth
of impoverished peri-urban areas around "mega-cities," of 10 million or more
people, that lack appropriate sanitation. Peru's recent
cholera outbreak is estimated to have cost the government $1
Recent reductions in mosquito-control efforts have left much of South America re-infested with the mosquito that transmits YELLOW FEVER. Consequently this viral disease threatens to reemerge as a major urban health problem with potential spread into Puerto Rico and the southern United States.
Recently a "foreign" mosquito has been imported into the United States. Aedes albopictus, also known as the tiger mosquito, is capable of transmitting viruses responsible for DENGUE FEVER and several forms of encephalitis. The mosquito was introduced to the United States in 1986 in used tires imported from Asia.
In the 1990's Russia underwent an epidemic of DIPTHERIA.
The construction of dams and water projects, with consequent alteration of water distribution patterns, often results in changes to mosquito vector populations. Construction of a dam in the Senegal River basin is believed to be responsible for the 1986 outbreak of Rift Valley fever (a viral infection transmitted by mosquitoes). Likewise, other dam and water projects have been implicated as factors contributing to snail-borne schistosomiasis outbreaks in Africa and the Middle East.
end - back
A New Disease
Called SARS -
Severe Acute Respiratory Syndrome
DIPTHERIA REMERGES... is an acute bacterial disease involving primarily the tonsils, pharynx, larynx, nose, and occasionally other mucous membranes of skin. Characteristic lesions are marked by a patch or patches of an adherent grayish membrane with a surrounding inflammation.
Diptheria was a common childhood disease in the 1930s, but a a vaccine against diphtheria has made it very rare in the US and other developing countries today where immunizations take place. The diphtheria toxoid was developed in 1921, came into use in the early 1930's, and into widespread use in the United States in diphtheria-pertussis-tetanus vaccine (DTP) from the mid 1940's.
Due to drastic land clearing and ecological changes diptheria is re-emerging without natural biological controls.
Diphtheria remains a serious disease throughout much of the world. In particular, large outbreaks of diphtheria occurred in the 1990s throughout Russia and the independent countries of the former Soviet Union. Most cases occurred in non-immunized or inadequately immunized people. Control measures have been implemented, but a risk of diphtheria remains in all these areas.
DENGUE FEVER (DF) is an acute, self-limiting febrile viral disease of 2–7 days’ duration, characterized by a sudden onset of fever and a variety of other symptoms such as severe headache, joint and muscular pain, retro-orbital pain, and rash. Occasionally, hemorrhagic manifestations, such as skin hemorrhages, gum bleeding, epistaxis, menorrhagia, and gastrointestinal hemorrhage, occur. Dengue hemorrhagic fever (DHF) is a more severe disease with fever, hemorrhagic phenomena, thrombocytopenia, and plasma leakage caused by increased vascular permeability. In patients with DHF, a sometimes-fatal circulatory failure with hypovolemic shock, called dengue shock syndrome, can develop.
DF is endemic in most countries in the tropical areas of southern and Southeast Asia, the Western Pacific regions, Central and South America, the Caribbean, and Africa. Transmission of DF increases during the rainy season. With an increased travel to tropical countries, and an increased incidence of DF in these countries), DF has become the most common imported arbovirus disease in Sweden. In the absence of an effective vaccine, pre-travel advice, mainly on protection against mosquito bites, is important to prevent the disease. In the light of changing travel patterns of humans updates on risk factors for DF are in order to form the basis for pre-travel advice.
In 1993, hantavirus pulmonary syndrome was first recognized in the southwestern United States. Cases have been found in 28 states; as of 1997, more than 164 cases had been confirmed in the United States and more than 400 throughout the Americas—the death rate has been approximately 45%. At the beginning of the investigation, serologic tests provided the first clue about the nature of the causative virus. Viral RNA was amplified from patient specimens, and a previously unknown hantavirus, now named Sin Nombre virus, was uncovered. Later, scientists from CDC, the University of New Mexico, and elsewhere found that several variant viruses were distributed over large areas of the United States, all previously unknown, all entrenched in specific rodent reservoirs, all capable of zoonotic transmission to humans.
It is now thought that hantavirus emerged, in part, from climatic and environmental conditions (i.e., increased rainfall) that favored an increase in rodent food sources, and consequently, an increase in the number of virus-infected rodents.
Bovine spongiform encephalopathy (BSE) in the United Kingdom may provide more lessons than any other recent emergent zoonotic disease episode. The disease was first diagnosed in the United Kingdom in 1986; as of 1997, more than 170,000 cattle had been reported as infected, but modern statistical methods have indicated that about one million cattle had been infected, roughly half of which entered the human food chain in the United Kingdom.
In 1995, the BSE agent was reported to be the cause of a new human zoonotic disease, new variant Creutzfeldt-Jakob disease. By 1997, 26 cases had been reported in the United Kingdom and one in France. A recent report from The Royal Society states that there is now a compelling case regarding new-variant Creutzfeldt-Jakob disease as the human manifestation of BSE.
Ebola hemorrhagic fever (Ebola HF) is a severe, often-fatal disease in humans and nonhuman primates (monkeys, gorillas, and chimpanzees) that has appeared sporadically since its initial recognition in 1976. The disease is caused by infection with Ebola virus, named after a river in the Democratic Republic of the Congo (formerly Zaire) in Africa, where it was first recognized. The virus is one of two members of a family of RNA viruses called the Filoviridae. There are four identified subtypes of Ebola virus. Three of the four have caused disease in humans: Ebola-Zaire, Ebola-Sudan, and Ebola-Ivory Coast. The fourth, Ebola-Reston, appeared in a primate research facility in Virginia, where it may have been transmitted from monkey to monkey through the air decimating the monkey colony.
The native host ("natural reservoir") of Ebola virus remains unknown. Research suggests that the virus is zoonotic (animal-borne) and is normally maintained in an animal host that is native to the African continent. The virus is not known to be native to other continents, such as North America. The incubation period for Ebola HF is from 2 to 21 days. The onset of illness is abrupt and is characterized by fever, headache, joint and muscle aches, sore throat, and weakness, followed by diarrhea, vomiting, and stomach pain. A rash, red eyes, hiccups and internal and external bleeding may be seen in some patients. Patients who die usually haven't developed a significant immune response to the virus at the time of death.
relative, the Marburg virus &
Marburg hemorrhagic fever is a rare, severe type of
hemorrhagic fever, affects both humans and non-human primates. Caused by a
genetically unique zoonotic RNA virus of the
filovirus family, first recognized in 1967,
with outbreaks in Marburg and Frankfurt, Germany and in Belgrade, Yugoslavia
(now Serbia). A total of 37 people became ill (lab workers, medical personnel,
and family members).
Cholera - is an acute, diarrheal illness caused by infection of the intestine with the bacterium Vibrio cholerae. The infection is often mild or without symptoms, but sometimes it can be severe. Approximately 1 in 20 infected persons has severe disease characterized by profuse watery diarrhea, vomiting, and leg cramps. In these persons, rapid loss of body fluids leads to dehydration and shock. Without treatment, death can occur within hours.
Cholera is contracted by drinking water or eating food contaminated with the cholera bacterium. In an epidemic, the source of the contamination is usually the feces of an infected person. The disease can spread rapidly in areas with inadequate treatment of sewage and drinking water. The cholera bacterium may also live in the environment in brackish rivers and coastal waters. Shellfish eaten raw have been a source of cholera, and a few persons in the United States have contracted cholera after eating raw or undercooked shellfish from the Gulf of Mexico. The disease is not likely to spread directly from one person to another; therefore, casual contact with an infected person is not a risk for becoming ill.