Originally published in The Ottawa Citizen October 18, 2004
Original Title: The HN factor
New information and reports of bird flu have shifted attention to the possibility of a new flu pandemic. The most lethal pandemic in our history occurred from 1917 to 1919 killing an estimated 20 million to 50 million people.
The World Health Organization (WHO) released a statement this month encouraging governments and pharmaceutical companies to begin production of bird flu vaccines.
To date there has not been any documented human-to-human transmission of the bird flu virus, but it is the high mortality rate for those who have caught it that has garnered attention. Millions of chickens have been killed during the past few years to contain the latest incarnation of the bird flu.
Why does the flu pose such potential danger, what are its origins and why does the vaccine change every year?
Imagine a beach ball with a small stick trapped inside it. Covering much of the beach ball’s surface is gritty sand. This is what influenza looks like under an electron microscope. The stick is the genetic material that infects us. The beach ball is the shell that protects the genetic material until it can invade our cells. The grains of sand represent the pieces of protein called antigens protruding out on the shell surface.
The antigens are designated with the “H” (hemagglutinin) and “N” (neuraminidase) monikers. For example, the bird flu has a designation of H5N1.
If our immune system is sufficiently primed for this viral invasion it will attack the antigens on the shell. The shell will break open and the immune system’s cells move in to destroy the genetic material before it causes disease. Our bodies develop immunity with each exposure to the flu virus and with each vaccination.
Many viruses slowly mutate or change over time. Most healthy people can adapt to these minor changes.
Epidemics and pandemics occur when the virus (usually Influenza A) undergoes a radical genetic change over a short time. This occurs when a human and bird virus both infect an animal simultaneously. The viruses swap genetic material, forming a new strain.
Because the immune system has never seen this new strain, it has no counter-measures to fight it; the body is defenceless.
Scientist Yoshihiro Kawaoka, of the University of Wisconsin-Madison and the University of Tokyo, looked into why the Spanish flu was so lethal. He stated, “We found that just one gene called HA, hemagglutinin, is sufficient to make a benign virus pathogenic.” The results of the study were reported in the journal Nature.
“One of the hallmarks of the 1918 Spanish flu is hemorrhage in the lungs,” said Mr. Kawaoka.
The suspicion is that the Spanish flu originated from birds. The research team wanted to look for clues within the genetic code of the virus that could help predict future lethal strains before they had a chance to spread.
Those most vulnerable are people over age 65, pregnant women, young children and those with chronic illnesses like asthma diabetes. Hospitalization rates for children under the age of two who have the flu are equal to those over 65.
The historical record of flu pandemics, the last in 1968, indicates a cycle of roughly 20 to 30 years; we are overdue. The WHO’s concern is that the world is unprotected against the bird flu virus, hence its recommendation for vaccine development.
The vaccine’s ability to protect you is determined by how closely they can match the strains that will arrive in North America each year. With a close match, protection rates against clinical influenza approach 70 to 90 per cent.
The flu vaccine contains dead viruses; it does not cause the flu. The vaccines cause side effects less than five per cent of the time. These commonly include a low-grade fever and fatigue for eight to 24 hours after immunization; minimal discomfort compared to the actual flu.
The vaccine is recommended for:
- Persons 65 years of age or older;
- Residents of nursing homes and chronic care facilities that house people with chronic medical conditions;
- Adults and children who have chronic heart and lung disorders, including children with asthma;
- Adults and children who with chronic diseases including diabetes mellitus, kidney failure, anemia or poor immune system function;
- Healthy pregnant women in their second or third trimester;
- And you!
Ottawa Public Health does not recommend the vaccine for people with:
- A previous allergic reaction to influenza vaccine;
- An allergy to eggs or thimerisol;
- A changing neurological condition;
- A history of Guillain-Barre Syndrome;
- A history of Oculo-Respiratory Syndrome.
Studies in the United States demonstrate marked cost savings to the health care system and increased work productivity. In one study, vaccinating working adults reduced absenteeism by 50 per cent.