|25 October 2004||Archive||Subscribe for free by E-mail or|
Each year, a new wave of deadly mutants sweeps over the Earth, killing hundreds of thousands of people. Science fiction? No, it's the flu. In about one out of ten of us each year, the influenza virus attacks the upper respiratory tract and causes a week or two of fever, muscle soreness, fatigue, headache, cough, sore throat, and runny nose--uncomfortable but hardly deadly. But for some, especially the elderly, the very young, and people with other illnesses (such as lung disease, cancer, diabetes, kidney problems, or heart disease), flu can cause pneumonia, complications of other illnesses, and death. Although the number of people killed by flu is very difficult to determine, estimates range from a quarter of a million to a million annually. In developed countries, these are mostly elderly, but areas with poor access to health care and with poor nutrition might suffer more deaths in young children.
You may wonder: if the flu vaccine provides protection, why do so many people die of flu? One reason is mutation. After vaccination against a certain strain of influenza virus, our immune system can detect that strain by the shape of the haemagglutinin and neuraminidase proteins on the surface of the virus. The immune system can then quickly respond to fight infection. The viral genes that make haemagglutinin and neuraminidase mutate easily, changing the shape of the proteins so that our immune system no longer recognizes and fights the infection. That is why a new flu vaccine is designed each year--so that the new strains can be targeted. Notice the word "strains"; there are often several different strains at any time, and the flu vaccine targets the three most dangerous of them. Flu is very infectious and can spread quickly, but it takes months to make a new vaccine, making it difficult for vaccine makers to predict which strains will predominate when the vaccine is ready. If unexpected strains spread, the vaccine may not protect against them. In practice, vaccines against the strains chosen by the World Health Organization (WHO) each year can prevent about two-thirds of influenza virus infections.
Another reason flu kills is that most people are not vaccinated, particularly in poor countries. For example, in Romania in 1997, only enough vaccine was distributed for 1% of the population, and in the Czech Republic and Poland the figure was only 2%. In an outbreak of flu in the Indian Ocean island nation of Madagascar in 2002, largely in Fianarantsoa Provice, 754 flu deaths were reported, but 95% of deaths were not in hospitals and were not investigated. In one district in that province, acute respiratory infection was most deadly in the elderly, but the largest number of deaths were of children under 5. A WHO report noted that factors including "unavailability of influenza vaccine, and lack of awareness about influenza" exacerbated the outbreak. In the United States this year, the supply of flu vaccine was cut roughly in half by a contamination problem in its manufacture, prompting worries of a shortage, although in 1997 enough vaccine was distributed in that country for nearly 30% of the population, more than twice the rate for developed countries in Europe and Asia.
Flu can sometimes become more virulent, as we will see in the next issue's article: "The Deadliest Fall."
Several decades ago, the number of people was growing rapidly as better health care and food production lowered the death rate. The Green Revolution boosted agricultural yields in developing countries. India and China no longer suffered famines, but produced food surpluses. Vaccination eliminated smallpox and reduced polio and measles. Oral rehydration therapy (a mix of salts and sugar similar to Gatorade) began to decrease deaths from diarrhea, which as recently as 1990 was the second leading cause of disability-adjusted life years lost. Mosquito control helped prevent malaria. All these developments helped more children survive the perilous first few years of life.
Great news, huh? But all the extra people surviving or being born added up to billions on an already overcrowded planet. A population bomb was exploding, and the aftermath was predicted to include environmental destruction and shortages of food, water, and other resources. There seemed little that could be done to stop the trend since a vicious circle was helping to fuel it: poor families having many children, who grow up poor and thus also have many children. Several factors may contribute to this circle:
Nations that had already gone through development had emerged with fairly stable, even shrinking populations, but the process had taken centuries, during which economic development had come with gradual health improvements, giving the population several generations to adjust to a new equilibrium of longer life and fewer births. In contrast, developing countries were suddenly confronted with a plummeting death rate. Would the birth rate catch up (or rather, down), or would the vicious circle of poverty and high birth rate lock much of the world into poverty?
Due to this story's length, it will be continued in the next edition of Human News.
In elections planned for January, 12 million Iraqis would choose a 275-member constitutional assembly that would appoint an interim government and write a constitution. Parties would receive assembly seats in proportion to their share of votes.
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