Infection outbreaks, unique diseases on the increase since 1980
as an increase in the number of cases of disease beyond what would normally be expected in a defined community, geographical area, or season,” Ramachandran said.
Between 1980 and 1985 there were well under 1,000 such instances, but for 2005-10, the number surged to nearly 3,000. In those same timeframes, the number of unique diseases causing the trouble climbed from less than 140 to about 160.
Of course, Smith and her colleagues reasoned, the increase could be due to factors such as better reporting of outbreaks and information sharing. To account for that, they paired the outbreak data with data on each country’s GDP, press freedom, population size, population density, and even Internet use (after 1990). Even after controlling for those factors, the numbers of outbreaks and unique causes rose significantly over 33 years. They also included latitude because previous studies had shown there are more infectious diseases in lower latitudes.
The infection Top 10
From the analysis, the researchers were not only able to track trends in the total number of outbreaks in each country and around the world, but they could also analyze the host source of the outbreaks. They compiled top 10 lists for each decade of diseases causing the most outbreaks.
For zoonoses in 2000-10, salmonella topped the list followed by e. coli, influenza A, hepatitis A, anthrax, dengue fever, shigellosis, tuberculosis, chikingunya, and trichinosis. Notably, chikingunya, a painful mosquito-borne virus that has afflicted much of the Caribbean and Central America, was a newcomer in the decade. So was influenza A.
Meanwhile, diseases that were top 10 scourges of earlier decades dropped off the list: campylobacterosis, cryptosporidiosis, and hepatitis E.
Among human-specific infections, gastroenteritis led the 2000s list, trailed by cholera, measles, enterovirus, bacterial meningitis, legionellosis, typhoid and enteric fever, rotavirus, mumps, and pertussis (whooping cough). Notable “newcomers” were mumps and pertussis, but adenoviruses and rubella had fallen out of their former prominence.
Smith said it is certainly good news that although the world seems to face an increasing number of infectious flare-ups from a widening range of tiny foes, we are improving our public health and medical defenses as well.
“Our data suggest that, despite an increase in overall outbreaks, global improvements in prevention, early detection, control, and treatment are becoming more effective at reducing the number of people infected,” the authors wrote.
The analysis continues. Smith, who teaches in the Department of Ecology and Evolutionary Biology, is particularly interested in how global infectious disease patterns will shift with climate and land use change.
“A warmer world, a world with altered landscapes, and a more urban world will undoubtedly have a new disease-scape to consider,” she said.
Top 10 human diseases 2000-10
(outbreaks during the decade)
- 381 gastroenteritis (viral)
- 251 cholera
- 246 measles
- 175 enterovirus infection
- 130 meningitis (bacterial)
- 117 legionellosis
- 106 typhoid and enteric fever
- 67 rotavirus infection
- 66 mumps
- 63 pertussis
— Read more in Katherine F. Smith et al., “Global rise in human infectious disease outbreaks,” Journal of the Royal Society - Interface 11, no. 101 (6 December 2014) (doi: 10.1098/rsif.2014.0950)
