Flu (Influenza): H1N1 Swine Flu and Seasonal Flu
What is the flu?
The flu is a common infectious disease caused by influenza (flu) viruses. The flu usually affects a person's breathing system. Seasonal flu generally occurs in the fall and winter and is caused by human influenza viruses. This year a new strain of flu virus was found, known as H1N1 swine flu.
What is H1N1 swine flu?
H1N1 swine flu is a new influenza virus that has caused illness in people worldwide. It was first detected in people around April 2009 and has been declared a pandemic.
How does the flu spread?
Both seasonal flu and H1N1 swine flu spread through tiny wet drops produced when a person coughs, sneezes, or talks. A person can get the flu by breathing in these wet drops, or by touching items and surfaces covered with these drops and then touching their mouth, nose, or eyes.
When can someone spread the flu to others?
People who have seasonal flu or H1N1 swine flu may be able to spread it to others about 1 day before getting sick to 5 -7 days after. Children and people with weak immune systems can spread the flu virus longer. However, people are most contagious during the first three days of illness.
How can I protect myself from the flu?
Use Healthy habits:
Is there a vaccine?
Yes. It is important for everyone to get a seasonal flu shot and an H1N1 swine flu shot this fall and winter. Vaccine is in short supply and is slowly becoming available. Contact your provider for updates on where you can get the vaccine. For more information on where to get a flu vaccine and frequently asked vaccine questions click here.
Do I need to wear a mask?
People who feel well do not need to wear a mask. People who feel sick may be asked by their doctor to wear a mask while in the doctor's office or clinic. People who are sick may choose to wear a mask when around others.
What are signs and symptoms of the flu?
The usual signs and symptoms of both seasonal flu and H1N1 swine flu are cough, sore throat, runny or stuffy nose, body aches, headache, chills, and feeling very tired. Most people also have a fever. Others may throw-up and have diarrhea.
Is it a cold or the flu?
In general, the flu is worse than the common cold. Colds are usually milder than the flu.
| Symptom | Flu | Cold |
| Fever | Usually 102 degrees F, but can go up to 104 degrees F and usually lasts 3 to 4 days. | Rare in adults and older children, but can be as high as 102 degrees F in infants and small children. |
| Headache | Sudden onset and can be severe
| Rare
|
Muscle Aches
| Usually, and often severe
| None or mild
|
| Tiredness and Weakness | Can last 2 or more weeks | Mild |
| Extreme Exhaustion | Sudden onset and can be severe | Never |
| Runny Nose | Sometimes | Often |
| Sneezing | Sometimes | Often |
| Sore Throat | Sometimes | Often |
| Cough | Usually, and can become severe | Mild to moderate |
How serious is H1N1 swine flu?
Both seasonal and H1N1 swine flu do not usually cause serious problems. Occasionally they can cause severe disease. Some people have had to go to the hospital and a small number of people have died. Historically, seasonal flu causes about 36,000 deaths in the United States each year.
How many people have been infected with H1N1 swine flu?
The exact number of people who have H1NI swine flu is unknown because usually symptoms are mild and testing is not needed. However, some hospitalized patients with specific symptoms are being tested. Click on the links below for more information:
Who is more likely to get very sick with the flu?
The list of "high-risk" people is similar for H1N1 swine flu and for seasonal flu:
- People with lung disease like asthma
- People with other medical conditions like diabetes, heart disease, kidney or liver disease, blood cell disease including sickle cell, or neurological disease that affects swallowing or breathing
- Pregnant women and women who have given birth within 2 weeks
- Children age 2 years and under
- Adults age 65 years and over
- People with weak immune systems (due to disease or medicines)
What should I do if I am sick with a flu-like illness?
See our recommendations on what to do if you are sick and when to contact your health care provider.
Will public gatherings, schools, or businesses be closed?
Most likely not. It is extremely unlikely that schools, public transit, public gatherings, or public areas will be closed. San Francisco is closely watching the situation, is taking steps to vaccinate as many people as possible and taking other steps to slow the spread of infection like having everybody use healthy habits and encouraging people ill with the flu to stay home until 24 hours after their fever is gone.
Should I travel?
Please visit the CDC H1N1 swine flu travel web page for guidance.
Additional information