The Flu
The flu is spread largely by droplet (aerosol) infection from individuals with a high viral level in their nasal and throat secretions, sneezing and coughing on anyone close at hand. The aerosol droplets of the "right" size (thought to be about 1.5 micrometers in diameter) remain airborne and are breathed into the nose or lungs of the next victim. Situations in which people are crowded together are more common in cold or wet weather--and so perhaps this contributes to spreading the flu at these times. It is interesting that in equatorial countries, flu occurs throughout the year, but is highest in the monsoon or rainy season.
Several recent developments promise to increase our understanding of flu. There are now drugs for influenza (neuraminidase inhibitors) that will potentially treat all strains of this virus; and new tests in development will provide an on-the-spot diagnosis in 15 minutes or less. These advances should lead to flu being accurately diagnosed and treated in the community. This new focus on flu should provide more reliable worldwide data on its incidence and spread.
Microbe Dispersal
A surprising number of microorganisms -- 99 percent more kinds than had been reported in findings published just four months ago -- are leaping the biggest gap on the planet. Hitching rides in the upper troposphere, they're making their way from Asia across the Pacific Ocean and landing in North America.
For the first time researchers have been able to gather enough biomass in the form of DNA to apply molecular methods to samples from two large dust plumes originating in Asia in the spring of 2011. The scientists detected more than 2,100 unique species compared to only 18 found in the very same plumes using traditional methods of culturing, results they published in July.
It's been estimated that about 7.1 million tons (64 teragrams) of aerosols -- dust, pollutants and other atmospheric particles, including microorganisms -- cross the Pacific each year. The aerosols are carried by wind storms into the upper reaches of the troposphere. The troposphere, the layer of air closest to earth up to about 11 miles (18 kilometers), is where almost all our weather occurs.
Cells can also interact with their high-altitude environment, for example, becoming the nucleus for rain drops and snow flakes and influencing the amount of precipitation that falls. Other scientists estimate that 30 percent of global precipitation stems from microbes.
Air Quality
Air pollution includes all contaminants found in the atmosphere in the form of gases or particulates and particles of biological origin. Fuel combustion is the primary source of a large number of health-damaging air pollutants, including fine and respirable particulate matter (PM2.5 and PM10), carbon monoxide (CO), sulfur oxides (SOx), nitrogen oxides (NOx), volatile organic compounds (VOCs), ozone (O3), atmospheric toxic metals such as lead, persistent free radicals and radioactive pollutants. In addition to chemical pollution, microbial air pollutants can include viruses, bacteria, fungi and their spores, lichen fragments, protists, spores and fragments of plants, pollen, small seeds and invertebrates.
Because it is located in the atmosphere, air pollution can travel over long distances affecting remote and pristine areas. As a result, air pollution has raised special concern due to its diverse serious consequences to the health of human beings (e.g. respiratory illness) and natural ecosystems (e.g. loss of biodiversity) on a global scale. Estimations indicated that about 100,000 deaths a year could be linked to ambient chemical air pollution in cities in the WHO European Region, shortening life expectancy by an average of a year. In addition, air microbiota can also directly impact human health via pathogenesis, the exposure of sensitive individuals to cellular components (e.g. pollen and fungal allergens and lipopolysaccharide), and the development of sensitivities (i.e. asthma) through prolonged exposure.
