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- First encountered in Ebola village, Congo, in the 1950s. Since then, minor, sporadic outbreaks
have killed from 100 to 280 people at a time across
Central Africa, mostly in Zaire (current D.R.Congo) and neighboring Uganda.
- In the early 2000s, rebel groups in Guinea displaced many people and also cut down biodiverse forests
to sell the timber. The fruit bats and human refugees were squeezed out of their habitat
and often came into contact in crowded refugee camps. In 2014, an outbreak of Ebola in Guinea spread to 5 nearby countries,
infecting about 26,000 people and also gorillas and chimpanzees. It then spread to overcrowded
urban slums, including the national capitals of Guinea, Sierra Leone, and Liberia, causing
over 11,000 deaths.
Burial customs (hugging dead relatives) greatly added to the danger of transmission.
The outbreak finally subsided in early 2016.
- A new outbreak began in August, 2018
in the eastern highlands of the Democratic Republic of Congo. It was small at first, and health officials were able to contain this outbreak to
fewer than 600 cases (including 320 deaths) during 2018 because it affected
small villages only and no big cities, making it easier
to trace and vaccinate all known contacts of infected persons. Unfortunately, anti-government rebel groups have become
active in this area, and many people are distrustful of government workers and of the medical workers (mostly from
international agencies) that have come to help. Several Ebola clinics have been attacked, and some medical agencies
(including Medecins Sans Frontiers, also called Doctors Without Borders) have withdrawn from the conflict zone bordering
neighboring Uganda. As of May 2019, over 1500 cases have occurred, with over 1000 deaths, and the disease has spread
to the city of Butembo (pop. 670,000, comparable to Boston or Memphis).
- Two monoclonal antibody treatments were approved in 2021.
- Even though an effective vaccine is available, effective control of the epidemic has not yet been achieved.
In 2021, the epidemic seems to have subsided in the D.R.Congo, but a new epidemic has begun in Cote d'Ivoire.
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Named after Zika forest in Uganda, where it first appeared in 1947.
In many people, symptoms are mild to absent, so precautions are not taken, allowing
the disease to spread. In others, Guillain-Barre Syndrome can occur as a devastating (sometimes fatal)
side effect. In pregnant women infected with Zika, the disease can spread to the developing
fetus and cause neurological defects such as underdeveloped brains (microcephaly).
To prevent transmission, the most important precaution is to avoid exposure to
mosquitoes, particularly Aedes aegypti. Precautions are especially important if you travel
to a region (such as Brazil or the Caribbean) where Zika already occurs.
In 2015-2016, an outbreak spread from Brazil to other parts of the Americas including
the Caribbean (especially Puerto Rico) and also back to Africa and to Hawaii. Cases have
occurred in most tropical countries (but not at high altitudes).
All reported cases of Zika in the mainland United States (as of January 2019) are from travelers
who visited Zika-affected areas, except for one laboratory worker who contracted Zika
from a needle-stick injury.
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Formerly widespread (14,000 people died across Europe in early 20th century), but
largely gone from U.S. by 2000 because of widespread vaccination.
In the early 2000s there were a few dozen cases in California, mostly among unvaccinated people.
In 2014, an outbreak centered at first in Disneyland (near Los Angeles) and spread to 7 states.
Most of the 140 people affected in California were unvaccinated for "philosophical" objections
including fear of vaccination. Medical authorities have long insisted that the dangers of
being unvaccinated are hundreds to thousands of times greater than any risks from the vaccine itself.
Beginning in early 2019, outbreaks occured in several states (Washington, California, and especially New York)
among communities where many people were unvaccinated. The disease then spread across 23 states
and several foreign countries (including Israel, Ukraine, and the Philippines).
As of May 2019, there are over 750 cases in the United States, mostly among children (several of whom have died),
and the outbreak is not yet controlled.
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