College of American Pathologists
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  H1N1 Information


Updated September 8, 2009

What is H1N1 (formerly known as swine flu?)
Novel H1N1 (referred to as “swine flu” early on) is a new influenza virus causing illness in people. This new virus was first detected in people in the United States in April 2009. This virus is spreading from person-to-person worldwide, probably in much the same way that regular seasonal influenza viruses spread.1

What are the symptoms of H1N1?
The symptoms of H1N1 are similar to seasonal flu and can include:

  • Fever
  • Cough
  • Sore throat
  • Body aches
  • Headaches
  • Chills and fatigue
  • Sometimes, diarrhea and vomiting.

Who is at risk for contracting H1N1?
Children (6 months to 17 years of age), young adults (18 to 24 years of age), and pregnant women are at greater risk for a developing H1N1. In addition, people with an underlying medical condition, such as diabetes, heart disease, asthma, and kidney disease, are also considered “high risk”.

One thing that appears to be different from seasonal influenza is that adults older than 64 years do not yet appear to be at increased risk of novel H1N1-related complications thus far.2

How is H1N1 diagnosed?
Your doctor might suspect that you have influenza, either seasonal or novel H1N1, based on your symptoms and what is circulating in your community. To confirm the diagnosis, laboratory tests might be performed in your doctor’s office, a hospital laboratory, or at the public health laboratory.

What is the role of the pathologist in diagnosing H1N1?
Pathologists are doctors who examine cell, tissues, and body fluids to diagnose infectious diseases, including H1N1 influenza.

Who should be tested for H1N1?
If you get sick with flu-like symptoms, stay home, limit contact with others, and call your doctor. Your doctor will decide if testing or treatment is needed. Tests may include a nasal swab to detect influenza A – this is best to do within the first 4-5 days of getting sick. Antiviral therapy may be prescribed and this is most effective when started within 24 – 48 hours of becoming ill.

How is H1N1 treated?
The H1N1 virus has responded to oseltamivir (Tamiflu) and zanamivir (Relenza) – both antiviral drugs. These treatments are most effective if started within the first 48 hours of symptom onset.

Can I be vaccinated for H1N1?
A vaccine for H1N1 is expected to be available in mid-October and may require two shots, the second shot three weeks after the first. The seasonal flu vaccine does not protect against the 2009 H1N1 flu. However, pathologists, the doctors who diagnose the infectious diseases, encourage Americans to receive the flu vaccine to protect themselves from the seasonal flu.

What is the role of the pathologist in developing vaccines?
Pathologists participate in vaccine development by collecting and characterizing the strains for inclusion in the following year's vaccine. This process starts with specimens sent to the clinical laboratory.

How are U.S. public health agencies notified of possible H1N1 cases?
In 2001, the College of American Pathologists (CAP) partnered with the CDC and the Association of Public Health Laboratories (APHL) to create a Laboratory Preparedness Exercise, which tests the strength of the Laboratory Response Network (LRN).

The LRN is a system of designated laboratories established to enhance early detection and surveillance activities, as well as increase laboratory response capacity associated with a potential pandemic or bioterrorism threat. In the United States, the LRN—a system of 1,500 laboratories throughout the 50 states—enables earlier detection of flu cases and allows public health agencies to investigate sources of infection more quickly and, therefore, more effectively respond with control and prevention activities.

How is the performance of medical laboratory tests monitored?
The College’s Proficiency Testing (PT) program is the largest laboratory peer comparison program in the world, routinely helping laboratories evaluate their performance and improve the accuracy of the patient results they provide.

Four of these PT programs test proficiency in influenza testing, although not specifically for the swine flu strain. The College data about the capability of U.S. labs to detect influenza A indicate a high degree of proficiency among America’s labs, and laboratory testing for influenza is the key to quickly detecting disease and protecting public health.

How can I protect myself and my family from H1N1?
Practicing good hygiene is good line of defense to protect yourself and your family from H1N1. Take these everyday steps to protect your health:

  • Cover your nose and mouth with a tissue when you cough or sneeze. Throw the tissue in the trash after you use it.
  • Wash your hands often with soap and water, especially after you cough or sneeze. Alcohol-based hand cleaners are also effective.
  • Avoid touching your eyes, nose or mouth. Germs spread this way.
  • Try to avoid close contact with sick people.
  • If you are sick with flu-like illness, the Centers for Disease Control and Prevention recommends that you stay home for at least 24 hours after your fever is gone except to get medical care or for other necessities. (Your fever should be gone without the use of a fever-reducing medicine.) Keep away from others as much as possible to keep from making others sick.3

How does H1N1 spread?
The H1N1 virus is thought to spread the same way as the seasonal flu – through coughing and sneezing by people with influenza. Sometimes people may become infected by touching something – such as a surface or object – with flu viruses on it and then touching their mouth or nose.

How many cases of H1N1 have been reported?
On June 11, 2009, the World Health Organization (WHO) announced that a pandemic of H1N1 was underway. On August 24, the President’s Council of Advisors on Science and Technology released a report stating that the H1N1 flu virus could cause up to 90,000 U.S. deaths, mainly among children and young adults.4 The outbreak could occur as early as September around the time that school starts, and the peak infection may occur in mid-October.5

Updated information regarding the number of confirmed cases in the United States can be found on the CDC’s Website.

Updated information regarding the number of global cases can be found on the WHO Website.


  1. Centers for Disease Control and Prevention
  2. Centers for Disease Control and Prevention
  3. Centers for Disease Control and Prevention
  4. President’s Council on Advisors on Science and Technology ,
  5. President’s Council on Advisors on Science and Technology ,