Vaccination programs against H1N1 swine flu are under way in the United States, China and Australia and will begin soon in parts of Europe. As people await their chance for immunization, below are some questions and answers about flu symptoms and what to do if they arrive before the vaccine does.

WHAT IS INFLUENZA AND WHAT ARE THE SYMPTOMS OF H1N1 SWINE FLU?

Influenza is a virus that infects the nose, throat and lungs. Seasonal flu typically kills 250,000 to 500,000 people globally, mostly the elderly, but also very young children, pregnant women and people with chronic diseases.

Most H1N1 symptoms are the same as seasonal flu: fever, coughing or sore throat, runny or stuffy nose, headaches, body aches, chills and fatigue. But swine flu also can cause vomiting and diarrhea.

WHAT IF SOMEONE GETS SICK?

People who are infected with the H1N1 virus may be contagious as early as one day before they show symptoms. Because H1N1 is the overwhelming flu strain circulating globally, health authorities say anyone with influenza should assume it is the swine flu. Quick flu tests may not detect H1N1, so doctors are advised not to bother testing people with flu-like symptoms.

Officials recommend frequent hand-washing, covering coughs and sneezes, and in some cases use of face masks to avoid spreading infection. The main remedies for mild illness are rest and ample fluids such as water, broth, sports drinks or electrolyte beverages made to prevent dehydration in small children.

WHAT IF SOMEONE GETS REALLY SICK?

Medical attention is recommended if the sick person has difficulty breathing or chest pain, appears blue or purple around the lips, vomits and cannot keep liquids down or shows signs of dehydration including dizziness.

The government recommends that people with chronic conditions who come into contact with an H1N1 patient seek treatment with antiviral drugs such as oseltamivir, which Roche AG and Gilead Science sell under the Tamiflu brand name, or zanamivir, an inhaled medicine produced as Relenza by GlaxoSmithKline.