SIGNS and SYMPTOMS
The onset of symptoms is usually abrupt and usually consists of fever, shaking chills, headache and muscle aches. Sore throat, runny nose and a dry cough are other common symptoms. Patients often have high fever and in severe cases will have an increased respiratory rate and pneumonia on chest X-ray. The virus itself can cause lung damage that leads to low oxygen levels in the blood. In addition, the damage to the lung airways makes it easier for bacteria to invade the lung and cause pneumonia. Influenza usually is more severe in the elderly and is associated with a death rate of nearly 3% in this group. The Avian flu strain has been reported to have much higher mortality rates and to be severe in younger patients.
Both killed and live vaccines are available and should be administered to the elderly, health care workers, patients with chronic illnesses, pregnant women, and young children. The influenza vaccine needs to be given annually and is designed to protect against the most likely strain to cause disease in the current year. Specific anti-viral agents (neuramidase inhibitiors and M2 inhibitors) can prevent or lessen the severity of disease if given during within 48 hrs of the first symptom. The Influenza strain causing disease this year is resistant to the M2 inhibitors (amantadine and rimantadine); therefore only the neuramidase inhibitiors (zanamivir given by inhaler and oseltamivir taken by mouth) should be used for 2005-2006 influenza infection.
CAUSES and RELEVANCE to FLORIDA
Influenza is caused by an RNA virus. There are two major strains, Influenza A and B. Influenza A is able to cause severe world-wide disease (called pandemics). The surface coat of the virus changes each year, and these changes, called antigenic shifts, allow the virus to infect those who have no immunity to the new virus type (unvaccinated individuals). Recently, an Influenza A strain that infects birds (avian flu) has spread from birds to some humans in Southeast Asia. Fortunately, at the present time the virus cannot spread from person to person, however experts fear that this virus will soon attain this capability. Because Florida is a major tourist destination, there is a high risk that foreign tourists could bring Influenza to our state. Florida is also major destination for migrating birds during the winter, and infected birds from other continents could quickly spread the virus to our bird population. Bird to human spread could then begin, and given the proper mutations, the virus could then develop the ability to spread from human to human and cause an influenza epidemic in our state.
Avoidance of crowded indoor environments is advisable to during Influenza season. The virus can be spread via small droplets released during coughing, sneezing and even talking. Individuals with possible Influenza should be encouraged to stay home from work until their symptoms resolve or markedly improve. Timely annual vaccination is critical for preventing infection. The vaccine is inexpensive, safe and in most individuals protects or markedly reduces the severity of Influenza.
Prepared by Frederick Southwick, M.D.
Professor of Medicine and Chief of Infectious Diseases
University of Florida College of Medicine
For more information see Infectious Diseases in 30 Days, McGraw-Hill, 2003, pg 459-462.