Swine flu is pandemic, the World Health Organization (WHO) has declared.
The declaration does not mean that swine flu -- aka novel influenza 2009 type A H1N1 -- is any more deadly today than it was yesterday.
A pandemic sounds scary. But what does it really mean? Here are WebMD's answers to your questions.
What is a pandemic?
What does the WHO pandemic alert mean?
Why has WHO declared a pandemic now?
Has H1N1 swine flu become more dangerous?
Am I less safe now that swine flu...
Antibiotics. Medicines that treat infections by killing bacteria; they have no effect on viruses, like the flu.
Antibiotic resistance. A condition in which bacteria adapt to an antibiotic medicine and become immune to it. This is a big concern due to prescribing antibiotics when they are not needed or effective.
Antiviral agent. Drugs that treat viral infections. Flu antivirals like oseltamivir phosphate (Tamiflu) or zanamivir (Relenza) can be used to treat the flu or to help prevent it in people at high risk. As a treatment, they work best if given within the first two days of the flu.
Bacteria. Microscopic one-celled organisms, some of which can cause illness.
Bronchitis. Inflammation of the airways leading to the lungs; it can be caused by viruses or bacteria. It can also be caused by irritants, including cigarette smoke.
Common cold. A viral infection of the upper respiratory tract; colds are unrelated to influenza.
Germs. Any microbes, including viruses or bacteria.
Immune system. The group of organs and specialized cells in the body that protect against disease.
Immunity. Protection from disease.
Immunization. A way of making a person immune to a disease; specifically by vaccination.
Influenza. Also called the flu, a common but sometimes serious viral infection of the respiratory tract. It can cause congestion, fever, body aches, and other symptoms.
Microbe. A microscopic organism.
Nasal vaccine. A vaccination, like FluMist, that is inhaled through the nose, rather than injected.
Pneumonia. Inflammation of the lungs, causing fever, chills, cough, chest pain, and difficulty breathing, that is often caused by a viral or bacterial infection.
Reye's syndrome. A life-threatening brain and liver disease that can follow infection with a virus, like the flu, and is most common in children. It’s often associated with taking drugs containing aspirin.
Sinusitis. Swelling of the sinuses, especially the ones around the nasal passages; it might be caused by infection with a virus or bacteria.
"Stomach flu." The informal name for gastrointestinal illnesses caused by any number of different microbes; it has no relation to actual influenza.
Vaccine. A substance, often given by injection, that helps protect against certain diseases; vaccines contain a dead or weakened version of a microbe, which spurs the immune system to recognize and destroy the living microbe during future infection.
Virus. A microscopic organism that invades living cells to reproduce; many, like influenza, cause illness. A virus is not affected by antibiotics.