Despite all the progress medicine has made over time, it has yet to conquer flu
Each year, over 600 million people (10 to 20 per cent of the world’s population) are infected with the flu. An annual flu shot is necessary to prevent influenza because the composition of the vaccine changes from year to year to match the strains of virus in circulation. In fact influenza viruses mutate so quickly that they can render one season’s vaccine ineffective by the next season.
Because the virus evolves with each new flu season, each year in September and February, respectively, the World Health Organization issues recommendations concerning the composition of the flu vaccine for the next season, which normally begins in May-June in the southern hemisphere and November-December in the northern hemisphere.
TYPES AND SUBTYPES: Of the three types of influenza viruses, (A, B, and C), types A and B are primarily responsible for epidemics in humans. Two subtypes of influenza type A are currently responsible for epidemics in humans: H3N2 and H1N1; H3N2 is associated with most deaths. No subtypes exist for the B virus.
The genetic makeup of influenza viruses allows frequent minor mutations on the surface antigens of the virus, known as “antigenic drift”, which can cause an epidemic because people are not protected against the new virus strain.
When a major change occurs, the process is known as “antigenic shift” and is the cause for great public health concern because it can lead to a worldwide pandemic (global epidemic). The most recent pandemic occurred in 1968 when the Hong Kong (H3N2) flu emerged. This strain completely replaced the previous one, which had circulated worldwide for 10 years. The Hong Kong flu pandemic caused over one million deaths globally.
HOW INFLUENZA SPREADS: Influenza is a highly contagious disease that often reaches epidemic proportions, for example during the winter months in Northern Hemisphere. It is easily transmitted from person to person in droplets by coughing and sneezing, through direct contact with an infected individual, or by touching contaminated surfaces. The virus enters the body through the nose or throat. The incubation period is usually two days but may vary from one to five days.
SYMPTOMS AND COMPLICATIONS: Symptoms include sudden onset of fever (usually high), headache, extreme fatigue, dry cough, sore throat, runny nose, and aching muscles. Symptoms last for one to two weeks. Flu can lead to serious complications in high-risk individuals such as the elderly, young children and persons with certain medical conditions. Complications caused by flu include bacterial pneumonia, dehydration and worsening of chronic conditions such as heart diseases, asthma or diabetes. A majority of hospitalizations and deaths due to influenza involve older adults and children below two years.
For most people, influenza involves an upper respiratory tract infection, that resolves spontaneously within several days with symptomatic treatment only.
Antiviral drugs for influenza are not important adjunct to influenza vaccine for the treatment and prevention of influenza. However, they are not a substitute for vaccination.
In severe influenza, admission to hospital, intensive care, antibiotic therapy to prevent secondary infection and breathing support may be required.
PREVENTION WITH AN ANNUALLY UPDATED VACCINE: The only best means of flu prevention is annual vaccination, which consists of an injection of one dose of inactivated vaccine, usually in the upper arm. The vaccine contains killed viruses that cannot cause influenza; it induces an immune response so that the body develops the necessary antibodies to ward off the flu.
THE GLOBAL INFLUENZA SURVEILLANCE NETWORK: WHO coordinates the Global Influenza Surveillance Network, which is in charge of tracking mutations in the virus. This network, created in 1952, is based on a partnership involving:
• WHO Collaborating Centres for Reference and Research on Influenza (WHO CCs)
• National Influenza Centres (NICs)
• Vaccine manufacturers
Globally there are four WHO Collaborating Centres, located in Atlanta, London, Melbourne and Tokyo, and 112 National Influenza Centres in 83 countries. The role of these centres is to gather epidemiological data and collect influenza specimens in their country.
The transmission of bird influenza virus plays an important role in setting off pandemics in other species, especially humans, so monitoring animal viruses is essential. The WHO’s Global Agenda on influenza focuses on broadening the surveillance of animal viruses and linking it with human virus surveillance.
INFLUENZA IN PILGRIMS TO MECCA AND MEDINA: The burden of flu among pilgrims has been underestimated. Only a small portion of pilgrims receive the influenza vaccine, in part due to a lack of knowledge about the vaccine and its benefits. Pilgrims must be made aware of the potential of contracting influenza during their Hajj and Umrah journeys in order to better protect themselves and other Hajj pilgrims.
Pilgrims should be vaccinated at least two weeks prior to their departure to Hajj.
WHO has set itself a clear goal to increase the number of elderly persons who receive the annual flu vaccine. Its objective is to reach a vaccination rate of 75 per cent for senior citizens in all countries by 2010.
In a study of over 285,000 people aged 65 or older during two flu seasons, flu vaccination was associated with a 19 per cent decrease in hospitalization for heart disease; a 16-23 per cent reduction in hospitalizations for stroke; and a 29-32 per cent decrease in hospital stays for pneumonia or influenza. In addition, the flu shot was associated with a 50 per cent reduction in the risk of death from all causes.
In people with chronic underlying diseases, influenza can lead to complications and hospitalization, cardiac and cerebrovascular diseases, exacerbation of chronic diseases and death. The influenza vaccine is recommended for persons who have one of the following conditions, which puts them at a particular risk:
ASTHAMA: Globally, rates of asthma have been rising for years. In the United States, the prevalence of this condition has more than doubled since 1980 and asthma now affects up to 15 million people, including six million children. While asthma does not predispose a person to flu, influenza represents a major complicating factor.
In asthmatic children, a study showed that flu vaccination decreased the risk of asthma exacerbations by between 22 per cent and 41 per cent. It also reduced the number of emergency room visits and hospitalizations for asthma. Despite the increased risk they run, fewer than 20 per cent of asthmatics are vaccinated against the flu.
CARDIOVASCULAR DISEASE: People with chronic heart disease and congestive heart failure are at increased risk of hospitalization and death, associated with influenza infection. They are included in the high-risk groups for whom annual vaccination is recommended. The flu shot is associated with a 19 per cent decrease in hospitalization for cardiovascular disease.
DIABETES: Influenza and pneumonia are reported to be the sixth leading cause of death among diabetics. Diabetics are about three times more likely to die of pneumonia or influenza-like illness, according to the US Advisory Committee on Immunization Practices. Death rates among diabetic patients increase by five to 15 per cent during flu epidemics.
The American Diabetes Association recommends that all patients with diabetes should be immunized against flu and pneumococcal disease, particularly those with complicating factors such as cardiac or renal disease, and patients who have been recently hospitalized.
CHRONIC PULMONARY DISEASE: Patients with chronic lung diseases are at an increased risk for serious complications of influenza and pneumococcal infections. Flu vaccination is recommended for adults and children with chronic lung diseases.
PREGNANCY: The severity of influenza and its complications increases after the first trimester of pregnancy. The risk of hospitalization for reasons that are attributable to influenza is the same for a woman in her third trimester of pregnancy as for a non-pregnant woman in one of the groups considered to be at risk for influenza. Therefore, women who will be in their second or third trimester during the influenza season are advised to be immunized to decrease the risk of hospitalization.
CHILDREN: The little ones are especially vulnerable to influenza. Infection rates are higher in children than any other age group with the highest rate found in children five to nine years old.
Often parents are not aware of the risk of severe flu-related complications for their children.
Today the youngest age group (one to three years) with high-risk condition is still under-vaccinated compared to older children (four to 18 years).
Here are a few basic rules children and parents can learn to help limit the spread of influenza:
• Cover your nose and mouth with a tissue when you cough or sneeze.
• Wash your hands often with soap and water, especially after you cough or sneeze.
• Avoid touching your eyes, nose and mouth. Germs are often spread this way.
In addition, children should be kept at home when they are ill to limit school epidemics.
• When to vaccinate: before the flu season starts. Ask your doctor for more information. The flu vaccine is an annual shot; it must be administered every year.
• Number of doses: two doses or half dose (according to the age) administered one month apart are recommended for children under age nine who are receiving influenza vaccine for the first time. For the others, only one dose or half dose is needed.
In addition to great social disruption, pandemics cause considerable economic losses in terms of health care costs and lost productivity.
WHO has developed an Influenza Pandemic Preparedness Plan that outlines the responsibilities of WHO and national authorities in the event of an influenza pandemic.
There have been several threats with pandemic potential over the last few years, making the occurrence of the next pandemic just a matter of time.
Despite all the progress medicine has made over time, it has yet to conquer flu
