Global disease outbreaks are on the rise, according to a new study, but fewer people are becoming infected. The communicable illnesses range from the exotic, including the current Ebola virus outbreak in West Africa, to more common strains of influenza, hepatitis and tuberculosis.
There have been more than 12,000 outbreaks around the world since 1980, affecting 44 million people.
The findings are based on information reported to the Global Infectious Disease and Epidemiology On-Line Network, or GIDEON, an international database that keeps track of outbreaks. It stores information on 215 infectious diseases in 219 countries. Outbreaks of disease that are quickly identified can be treated immediately and people who are suspected of being infected can be quarantined if necessary.
While the number of outbreaks is going up, the good news, according to Sohini Ramachandran, is fewer people are becoming infected today than in the past, "which might indicate that we are getting better as a society at large in preventing the spread of outbreaks once they start or identifying outbreaks rapidly."
A Brown University biostatistics expert, Ramachandran conducted the assessment of GIDEON data along with several colleagues. Their results were published in the Journal of the Royal Society Interface.
Most of the diseases reported to GIDEON, according to Ramachandran, first infected animals, then jumped the species barrier to humans. That is the case with the swine and avian flus and, most recently, the Ebola virus, which is thought to have originated in fruit bats.
“When animals are kept in really tight quarters with other animals, anything that is pathogenic among them can spread very rapidly. And then when humans are nearby, that pathogen can be transmitted to a human host," she said.
Ramachandran says increasingly dense population centers are setting the stage for a rise in unique disease outbreaks.
Researchers were also curious to learn if global warming was causing a rise in the number of infections. Ramachandran says it does not appear so.
“We are experiencing a more rich type of set of pathogens as a human species. But overall the burden of infectious disease outbreaks has been decreasing in the recent past," she said.
The top 10 animal-transmitted diseases between 2000 and 2010 were salmonella, E. coli, influenza A, hepatitis A, anthrax, dengue fever, dysentery, tuberculosis, chikungunya and trichinosis. So-called zoonotic diseases, according to the report, accounted for 56 percent of all disease outbreaks since 1980.
Examples of human-specific infections included cholera, measles, mumps and typhoid.
The study analyzed data collected between 1980 and 2013.