Childhood epidemics and the demographic landscape of the Aland Archipelago

Historically, the introduction of childhood diseases such as measles or smallpox resulted in the infection of nearly every susceptible individual in a community. While smallpox has long been considered the deadlier of the two childhood diseases, research has shown that the immune response to measles infection results in immune suppression that can last for weeks or even months. Higher mortality during measles epidemics has typically been associated with completely susceptible populations; however, in Aland, Finland--a population that experienced regular epidemics of both childhood diseases--mortality from all causes during the 1820-21 measles epidemic was 25% higher than that experienced during the 1823-24 smallpox epidemic. Excess mortality surrounding measles epidemics suggests that this disease may have larger impacts on the demographic history of populations than previously thought. This study uses archival records to investigate syndemic interactions between measles and other diseases during a 19th century measles epidemic in the Aland Islands, Finland. Comparisons to smallpox and a non-epidemic period indicated greater than expected mortality for individuals aged 5 to 9 years and over 50 years; though neither epidemic had long-term demographic consequences. These results are consistent with deaths from secondary infections due to measles-induced immune suppression, but not conclusive. The unknown impact of measles exposure on adults with antibodies, and the variety of other diseases and symptom descriptions, indicates that the possibility of co-occurring epidemics cannot be ruled out.