Another influenza pandemic is threatening the world. The World Health Organization  has already warned the governments to prepare for the worst as the Swine Flu spreads and claims the life of a baby outside of Mexico.

As your resident Doctor, it’s my social responsibility to educate everyone about the influenza. Taken directly from the Department of Health’s website, here’s the basic info about the virus.

1. What is flu?

Flu, or influenza, is a highly contagious acute respiratory illness caused by the Influenza virus. Flu season generally occurs annually all over the world, during the cold season (October to January).

Influenza infects over 30 million people in the U.S. each year, which is roughly 10% to 20% of the U.S. population. Flu and its complications is the sixth leading cause of death in the U.S., killing 20,000 – 40,000 people a year. As of 1997, it is the fourth leading causes of morbidity or illness in the Philippines. Flu is the most common cause of absenteeism in both school and work.

2. What causes flu?

Flu is caused by the Influenza virus that invades and multiplies in the respiratory tract. Influenza viruses are divided into three types: A, B, and C. This classification is based on the capability of their components to cause disease. Influenza types A and B are the primary causes of the disease and responsible for epidemic outbreaks. Influenza type C is a sporadic cause of predominantly upper respiratory tract disease such as the common cold and pharyngitis.

The influenza virus is unique in that its structure changes each year. Major changes cause worldwide epidemics called pandemics. Minor changes cause the annual local outbreaks. Pandemics are estimated to occur every 10 to 20 years while local outbreaks occur every 2 to 3 years.

In the pandemic of 1918 – 1919, the Influenza a virus caused over 20 million deaths worldwide. In 1997, an entirely new variety of human influenza virus surfaced and caused the Hong Kong bird flu in which one-third of the first 18 confirmed cases died.

Other viruses that known to cause flu-like illness are the respiratory syncyctial virus (RSV) and adenovirus.

3. Who are at risk of getting flu?

Any person is at risk of getting flu. The risks are higher if you belong to any of the following groups:

• Those who belong to extremes of age generally have low immune functions to fight the virus.
• Those with chronic debilitating illnesses (e.g., asthma, emphysema, kidney disease, diabetes).
• Smokers and chronic alcoholics with secondary liver dysfunction.
• Children in day-care centers and adoption homes.
• Children on long-term aspirin therapy.
• Women in their 2nd or 3rd trimester of pregnancy.
  Residents of nursing homes.

4. How do you get flu?

Flu is highly contagious and spreads through inhalation of air droplets containing respiratory secretions from persons with flu. These secretions are aerosols of viruses that contaminate the air, hands and surfaces of our environment. You can get these aerosols when the person with flu coughs and sneezes. You can even get flu when you handle objects contaminated by these secretions such as tissue paper.

The incubation period of flu is 1 to 4 days. Transmission through a community is rapid, with the highest incidence of illnesses occurring within 2 to 3 weeks of introduction, and with the outbreak lasting for 6 to 10 weeks.

5. How do you know that you have flu?

Once you get infected with the virus. It takes 1 to 4 days for you to feel symptoms due to the disease.

The most common signs and symptoms are:

• Headaches, muscle aches, joint pains, body malaise and fatigue that can be severe during the first few days but will slowly improve.
• Sore throat which is more common in older children (because young ones cannot complain) and adults.
• Cough which starts as dry and hacking and progresses by the 3rd day to wet with thick mucus. Your cough can worsen during the next 4-7 days and can last for over 2 weeks. You have a higher risk to develop bronchitis and pneumonia if you smoke.
• Fever with a temperature of 38oC to 40oC, with or without chills, within 12 hours from onset of infection. Fever is higher in children and can reach to as high as 41oC.
• Nasal congestion, watery eyes or runny nose.
  Vomiting and/or diarrhea. Diarrhea is more common in children less than 6 years of age.

6. What are the precautions to take to avoid flu?

The most logical way to avoid flu is for you to avoid persons with the disease. Adults with flu are typically contagious for 5-7 days from fever onset. In children, they are contagious for 7-10 days and even longer (up to 4 weeks) in patients with low natural defense mechanism.

However, since this is not entirely possible, a flu vaccine is available which can help give you immunity against flu. The vaccine has 70-90% efficacy and varies from year to year because the Influenza virus strains change every year. Flu shots are given each year so that you can get protection against newer strains of the virus.

Inquire from your physician about the availability of the flu vaccine. The vaccine is indicated for most individuals especially those included in the high-risk groups. You can have yourself vaccinated any time during the flu season. It takes one to two weeks for you to develop antibodies that provide protection against flu. The only time you should not get the vaccine is if you are allergic to eggs, which are a component of the vaccine of the vaccine, or thimerosal, which is the vaccine preservative.

7. How do you treat flu?

The treatment of flu is divided into nonspecific and specific treatment.

Non-specific treatment includes the following:

1. To prevent complications and to allow your immune system to work:

• rest
• comfortable room temperature
• increased fluid intake

2. Symptomatic drug treatment:

• For fever, headache, muscle and joint pains: Analgesic/Antipyretic agents – Paracetamol, Ibuprofen
• For runny and stuffy nose: cold Medications – Phenylpropanolamine
• For dry cough – Dextromethorphan
• For productive cough: Guiafenesin, Carbocisteine, Bromhexine, Ambroxol

Specific treatment for flu include:

1. Older agents that are very efficacious only against the Influenza A virus:

• Amantadine
• Rimantadine

2. Newer agents that are used for the treatment of Influenza A and B:

• Zanamir for inhalation
• Oseltamivir

One drawback against these drugs is their high cost. Side effects include headache, dizziness, insomnia, irritability, difficulty in concentrating, and anxiety.

Antibiotics should not be given unless there are bacterial complications.

8. What are the complications of flu?

Pneumonia and otitis media are the most common complications of flu. Otitis media can present as earache or fluid coming out of your ears. Pneumonia can manifest as high-grade fever, brassy cough, lack of appretite, drowsiness, difficulty in breathing, and increased phlegm and mucus production. These are usually viral in origin but oftentimes, secondary bacterial complications set in. When bacterial infection sets in, antibiotics are warranted. Prolonged muscle weakness and pain are less frequent complications. In rare instances, Reye’s Syndrome occurs. This is marked by delirium, seizures, stupor, coma, and death.

9. When should you call your physician?

Call your physician if you note the following:

• Fever recurs after it has gone for1-2 days, or you continue to have high-grade fever after 4 or 5 days.
• Cough becomes wheezy, with difficulty in breathing and the presence of bloody or yellow-green mucus and phlegm.
• You have chronic illness (e.g., asthma, cancer, diabetes, kidney problems) or your chronic condition worsens.
• Ear pain and/or ear discharge.
• Prolonged headache, confusion, frequent muscle twitching, seizures or convulsions and general body weakness.
• Bleeding in any part of your body.
• Rapid or irregular heartbeat.

About influenza pandemic

• “An influenza pandemic is a rare but recurrent event.” – WHO
• “A pandemic occurs when a new influenza virus emerges and starts spreading as easily as normal influenza – by coughing and sneezing. Because the virus is new, the human immune system will have no pre-existing immunity. This makes it likely that people who contract pandemic influenza will experience more serious disease than that caused by normal influenza.” – WHO

Past influenza pandemics

• first well-documented case was traced back to 1580
• 28 cases of influenza pandemic were recorded from 1580-1900
• since 1900-present, there have been at least 3 pandemics: Spanish Flu, Asian Flu, and Hong Kong Flu
  • Spanish influenza
    • occurred in 1918-1919, just as World War I was winding down
    • killed an estimated 40-50 million people worldwide (WHO estimates)
    • swept through North America, Europe, Asia, Africa, Brazil, and the South Pacific
    • considered one of the deadliest disease events in human history
    • caused by influenza type A virus (H1N1)
    • higher mortality rate among the younger population; people between 20-45 years old accounted for 60% of the fatalities
  • Asian influenza
    • occurred in 1957-1958
    • estimated 2 million deaths
    • first identified in China
    • caused by type A virus (H2N2)
    • outbreak occurred between late summer and fall
    • those mainly infected were above 55 years old
  • Hong Kong influenza
    • occurred in 1968
    • estimated 1 million deaths
    • arose in Southeast Asia (first detected in Hong Kong), then spread to the US and Europe
    • caused by type A virus (H3N2)