A bird's-eye view of avian influenza: although rare, the avian flu can manifest itself as conjunctivitis. You may be the first health-care professional to see an infected patient.(Patient Care)(Disease/Disorder overview)

Imagine this: An 8-year-old boy presents to your office complaining of pain in his left eye. His conjunctiva is obviously inflamed. In addition, his cheeks are flushed, and he has a raspy cough.

You take his history, and he tells you his eye began hurting the evening before last. You ask him about the day that lead up to that evening, and he excitedly tells you his third-grade class visited a farm three days prior. He denies any injury to the eye. Upon further questioning, the boy reports that his throat started feeling sore upon waking this morning. Also, he tells you that his arms and legs started feeling "achy" before he went to sleep last night. As you're about to examine the boy, one of your staff members interrupts to tell you in private that she has received seven calls thus far from parents reporting similar ocular pain in their children and in themselves.

While this scenario may seem like an outbreak of run-of-the-mill conjunctivitis, it is actually the beginning of an avian flu pandemic, something you may be faced with in the future (see "The Difference Between an Epidemic and a Pandemic," below).

The World Health Organization (WHO) projects that an avian influenza pandemic is expected to exhaust health-care resources, interrupt commerce and have a major economic impact. (2) As a result, the United States, along with many other countries and organizations, is actively preparing for the possibility of such a pandemic. Indeed, Congress has appropriated $334 million to support the global campaign against bird flu and $2.3 billion to prepare domestically for a possible influenza pandemic. (3,4)

The last three global influenza pandemics occurred in 1918, 1957 and 1968. The 1918 "Spanish" flu pandemic killed about 500,000 people in the United States and 50 million worldwide. (5) In 1957, the "Asian" flu killed about 70,000 in the United States, and the 1968 "Hong Kong" flu killed 34,000 people in the United States. (5)

Although rare, the avian flu has the potential to manifest itself as conjunctivitis. This means that you, the primary-care optometrist, may be the first health-care professional to see a patient infected with this dangerous illness. You may even be the first to encounter an infected patient who does not have conjunctivitis if the patient presents to you for his or her annual exam exhibiting flu-like symptoms.

To prepare you for the possibility of an avian flu pandemic, this article explains the influenza virus types and the components of the avian flu, and discusses how you can protect yourself, your staff and your patients from this dangerous illness.

Influenza Virus Types

There are three types of influenza viruses: A, B and C. Type C viruses are generally not a concern for humans because these infections are mild and do not cause epidemics or pandemics. Although very common, the type B influenza virus, normally found only in humans, is not a pandemic maker. Every year, 5% to 15% of the world's population experiences an infection of seasonal influenza--a B influenza virus, which has a relatively low mortality rate. This is the influenza for which flu shots are made.

Influenza A, known as avian influenza, primarily infects birds, but may infect people, pigs, horses and other animals. (6) When influenza A jumps the "species barrier," it has the potential to create a new virus for which humans have no immunity, thus producing a pandemic. Influenza type A viruses, unlike influenza type B and C, are divided into subtypes based on two surface glycoproteins: hemagglutinin (HA) and neuraminidase (NA).

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There are 16 different HA subtypes and nine different NA subtypes. (7) Influenza A viruses are classified according to their HA and NA proteins, such as H5N1, which has an HA 5 protein and an NA 1 protein. H5 and H7 subtypes of influenza type A are further classified as either highly pathogenic avian influenza (HPAI) or low pathogenic avian influenza (LPAI) based on the severity of the disease produced in birds. HPAI may kill 90% to 100% of infected chickens, while LPAI causes mild or no illnesses in infected chickens.

Because the disease mortality in birds may not correlate to its effects in people, it is currently unclear how the distinction between HPAI and LPAI relates to the risk of serious illness in humans. (8) To complicate matters, LPAI may evolve into HPAI viruses. Because all past …