Biology Reference
In-Depth Information
world's nations is that such an event could lead to a worldwide pandemic
reminiscent of the 1918 pandemic.
Excluding the possible transmission to humans and other mammals, as cur-
rently understood, the AI transmission loop involves migratory, sedentary,
and backyard birds and poultry. Migratory and sedentary birds first trans-
mit, or spill over, low pathogenic AI (LPAI) virus to poultry either directly or
through backyard birds. Domestic poultry then transmit, or spill back, HPAI
virus to other birds—including migratory birds—directly or indirectly. The
infected migratory birds, if still fit to fly, can then spread the virus to other
regions. A confounding factor to this cycle is that the avian influenza virus
is apathogenic to some species of ducks. Though they may appear unaf-
fected and healthy, ducks which are really infected but asymptomatic may
transmit the virus to other poultry and birds. Aside from migration, other
means through which HPAI H5N1 can spread includes transboundary and
in-country movement of poultry products and by-products, as well as legal
and illegal wild bird trades.
Avian influenza viruses survive well in water, especially at low tempera-
tures. In some areas, the virus may survive in water through the entire winter.
Therefore, water bodies and wetlands where wild birds and domestic birds
may mingle are a risk. Moreover, because the AI virus transmits through
fomites, areas near the transportation routes to where poultry farms domi-
nate are also considered at-risk. Other meteorological and environmental
parameters may have direct or indirect roles in promoting avian influenza
transmission. These parameters may influence, for example, the survival
of H5N1 virus, the availability of grazing fields for free range poultry, the
selection of refueling and molting areas, and the seasonal migration and
weather-induced movements for certain species. These meteorological and
environmental parameters can be conveniently derived from satellite data.
3.3 Remote Sensing as a Means of Acquiring
Environmental Information
Satellites offer continuous temporal and spatial observations of the Earth,
and provide an uninterrupted data flow pertaining to its climate and the
environmental conditions. Therefore, remote sensing is a vital technology
for studying the relationship between these conditions and infectious dis-
eases. In addition, anomalies and deviation from normal environmental and
climatic conditions that are observed in remote sensing data are useful for
assessing risks of infectious disease outbreaks. Several of the current Earth
observation satellite missions provide data products pertaining to the envi-
ronmental and contextual determinants of infectious diseases. Some of these
missions are summarized in the next sections.
