The relationship between brightness and measles transmission appeared even clearer at the local level, as did the potential value of the researchers' technique in providing medical treatment. In Niamey, measles cases were recorded daily for three districts, or communes, during the 2003-04 dry season. Brightness and measles infection both peaked early in the first and second communes in February and March of 2004.
A two-week mass-vaccination campaign was launched in March and April, but population density, as determined by light brightness, had already started to decline in communes 1 and 2, the Princeton-led team found. This means that because the vaccination was not synchronized with population-density increases in communes 1 and 2, large numbers of people in those districts may have left the city without receiving the measles vaccine, Bharti said.
Under similar circumstances, the researchers write, measurements of population density determined by nighttime imagery which can be ready to analyze within 48 hours of the satellite collecting the data could be used to help coordinate preventative and reactive treatment with periods when the most people are arriving or are present in a certain area.
Rohani said that the technique could become important in predicting the peak of measles outbreaks in other susceptible countries, but might also apply to other diseases that, like measles, are driven by population density more than any other factor.
"This is probably the most careful dissection of an epidemic of measles in any setting I'm aware of it's very careful work that provides a mechanistic explanation for the progression of measles in a large population," he said. "It also shows promise for understanding seasonality in places like Niger for other directly transmitted infectious diseases like meningococcal infections or pertussis, or maybe influenza."
The researchers also are explor
|Contact: Morgan Kelly|