Influenza

The first influenza virus was identified in the 1930's, although the disease has been recognized for many centuries. Influenza viruses exist in three forms: A, B and C.

• Type A is the most common and associated with the most serious epidemics and pandemics.

• Type B outbreaks can also reach epidemic levels, but the disease it produces is generally milder than that caused by type A.

• Type C either causes mild illness or no symptoms at all.

Influenza typically occurs in the winter months, with outbreaks lasting six to eight weeks. Unlike the common cold, the onset of symptoms is often very sudden and initial complaints include aches and pains, weakness, and chills. A fever soon follows, lasting about three to five days. Acute respiratory symptoms, like dry cough, are additional symptoms of influenza and are usually present for five to seven days. However, cough and weakness can persist for up to two weeks.

 Influenza infects more than 100 million people in the USA, Europe and Japan in an average year. On average, one in 10 adults and one in three children are affected by influenza each year. Worldwide epidemics, known as pandemics, are seen every 10 to 40 years. The most serious pandemic was the Spanish Flu between 1918 and 1919, which killed more than 20 million people. Influenza viruses A cause the most severe outbreaks. In the Middle East and Gulf States, Hajj season is particularly favorable to the virus spread. Besides, the extreme change in temperature between the outside (40 degrees plus) compared with strong air-conditioning indoors could also increase the risk of influenza during summer.

Causes and Risk Factors

Influenza is highly contagious and is primarily passed from person to person via droplets shed during coughing or sneezing. The influenza virus enters the body through the mucous membranes of the nose, mouth or eyes. The virus multiplies within four to six hours of infection with the incubation period ranging from one to seven days during which time the virus is already being spread.  

Diagnosis and Screening

Initial diagnosis is based on the presence of typical symptoms. Information obtained from surveillance activities helps to monitor and diagnose influenza levels and may be helpful in making a clinical diagnosis. Rapid diagnostic tests, using samples from throat swabs, nasopharyngeal washes or sputum, support surveillance activities, and can be particularly useful as a diagnostic tool outside of an influenza outbreak. 

Management

The options for the treatment of influenza have until recently been limited, with the vast majority of sufferers taking remedies, which only treat some symptoms and do not attack the viruses themselves.

Vaccines are available as a preventative measure for those at most risk of developing complications of influenza such as bronchitis and pneumonia. Influenza vaccination is recommended for:

• anyone over 75 years old
• residents of nursing homes
• adults and children with a chronic heart or chest complaint, including asthma
• Adults and children with diabetes or with lowered immunity due to disease or treatment, such as cancer treatment.

However, the effectiveness of vaccines can vary depending on how well the vaccine matches the viral strains circulating in a given influenza season and vaccination must be repeated annually.

Today there is a new class of medicine known as neuraminidase inhibitors, specifically designed to target the influenza virus directly.