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An international study led by the University of Toronto's Dalla Lana School of Public Health links the rise of tuberculosis (TB) in Zimbabwe during the socio-economic crisis of 2008-2009 to widespread food shortage.

Between 2000 and 2007, Zimbabwe underwent an economic collapse characterized by political crises, hyperinflation and a real GDP reduction of 40 per cent. After a controversial election, GDP fell a further 14 per cent in 2008. The researchers wanted to determine whether the widespread food shortage would weaken the immune systems of the population and lead to a rise in tuberculosis incidence.

The incidence of TB was assessed at two mission hospitals that remained opened during the crisis. Although geographically far apart, both hospitals demonstrated a rise in the number of TB cases as the hunger associated with the crisis worsened.

“This was the first study to detect the recent TB outbreak in Zimbabwe, and the first anywhere to suggest an association between rising TB incidence and national economic decline in the absence of armed conflict,” said Michael Silverman, assistant professor at the Dalla Lana School of Public Health and senior author of the study, published in PLOS ONE.

Although the same phenomenon may occur with other infectious diseases, the study focused on TB – one of the largest causes of morbidity and mortality in Zimbabwe, especially among people living with HIV.

"Zimbabwe may have been predisposed to this TB outbreak due to the presence of a large HIV-positive population who were particularly vulnerable to the effects of food shortages which led to malnutrition and further damage to already weakened immune systems," said Silverman.

Many developing countries have large HIV positive populations and thus socioeconomic instability could lead to a similar rise in tuberculosis rates elsewhere.

“This finding emphasizes the importance of adequate food availability in controlling TB incidence, particularly in areas with high HIV prevalence," Silverman said.

The study also demonstrated that TB incidence appears to be seasonal, with a larger number of cases when food is scarce in the dry season and lower numbers of cases post-harvest when food is more plentiful. Research data also suggests that TB incidence fell back to pre-crisis levels when the economy of the country and food security improved after 2009.

"Political instability can lead to economic instability, and this can lead to a health crisis with the most vulnerable people in society the most likely to be harmed,” said Silverman. “It is important for political leaders to be aware that in addition to economic costs, political conflict can potentially have very serious health implications for vulnerable communities."

The study was co-authored by: Stephen Burke of the University of Ottawa and Elliot Lass of the University of Toronto; Dr. Paul Thistle of ��˾��ֱ�� and the University of Zimbabwe; Arif Jetha, Shelly Bolotin and Andrew Simor of the Dalla Lana School of Public Health; Lovemore Katumbe of the Howard Hospital in Zimbabwe; Dan Schwarz of Brigham and Women’s Hospital and Children’s Hospital of Boston; and Jack Barker of the Murabinda Mission Hospital in Zimbabwe and King’s College Hospital in the UK.

Jelena Damjanovic is a writer with University Relations at the University of Toronto.