AIDS (Acquired Immunodeficiency Syndrome) is a chronic, life-threatening condition caused by the human immunodeficiency virus (HIV). By damaging or destroying the cells of your immune system, HIV interferes with your body's ability to effectively fight off viruses, bacteria and fungi that cause disease. This makes you more susceptible to certain types of cancers and to opportunistic infections your body would normally resist. In the more than two decades since the beginning of the HIV/AIDS pandemic, approximately 65 million people worldwide have become infected with HIV, including more than 25 million who already have died. If more is not done to fight the HIV/AIDS pandemic, it is on course to be one of the worst in history, with millions more people estimated to become infected by the end of this decade. The HIV/AIDS pandemic presents political, economic, public health, social and scientific challenges to nations worldwide.
Ebola virus: A notoriously deadly virus that causes fearsome symptoms, the most prominent being high fever and massive internal bleeding. Ebola virus kills as many as 90% of the people it infects. It is one of the viruses that is capable of causing hemorrhagic (bloody) fever.
Epidemics of Ebola virus have occurred mainly in African countries including Zaire (now the Democratic Republic of Congo), Gabon, Uganda, the Ivory Coast, and Sudan. Ebola virus is a hazard to laboratory workers and, for that matter, anyone who is exposed to it.
Infection with Ebola virus in humans is incidental -- humans do not "carry" the virus. The way in which the virus first appears in a human at the start of an outbreak has not been determined. However, it has been hypothesized that the first patient (the index case) becomes infected through contact with an infected animal.
Ebola virus is transmitted by contact with blood, feces or body fluids from an infected person or by direct contact with the virus, as in a laboratory. People can be exposed to Ebola virus from direct contact with the blood or secretions of an infected person. This is why the virus has often been spread through the families and friends of infected persons: in the course of feeding, holding, or otherwise caring for them, family members and friends would come into close contact with such secretions. People can also be exposed to Ebola virus through contact with objects, such as needles, that have been contaminated with infected secretions.
Influenza Pandemics: Annual flu epidemics kill 250,000-500,000 people each year and cause severe illness in 3 million to 5 million. But new strains that jump from animals to humans can be even more devastating if the global population has no immunity to the virus.
1957-58 "Asian flu"
First identified in China, this H2N2 virus caused roughly 2 million deaths worldwide. The virus is thought to have emerged after a human form of H2N2 combined with a mutant strain in ducks. The strain has not circulated in humans since 1968, so much of the global population has no immunity to the strain. Most of those who died were elderly.
1968-69 "Hong Kong flu"
The pandemic was first detected in Hong Kong. The H3N2 virus killed around 1 million people globally, with those over 65 most vulnerable. H3N2 viruses still circulate today.
1997 "Bird flu"
For the first time, an influenza virus was found to spread directly from birds to people. The H5N1 bird flu infections were linked to poultry markets. The first outbreak in Hong Kong killed six of 18 people infected. The World Health Organization has recorded 598 cases since 2003, with 352 deaths. Most deaths from bird flu are in Egypt, Indonesia and Vietnam and China. So far, the virus has not adapted to spread easily between humans.
2009 "Swine flu"
One of the new strains was the H1N1 "swine flu" virus that originated in Mexico in 2009. The virus, a combination of a Eurasian swine flu virus with another strain that was itself a mix of bird, swine and human flu virus. The strain went on to kill more than 18,000 people around the world.
2019-21 "COVID-19"
You know all about this one...