This paper examines the effect of Venezuelan displacement on the spread of 15 infectious diseases in Colombia. Official statistics suggest that by the end of 2018, when this analysis was undertaken, 1.26 million Venezuelans had migrated to Colombia with the intent to stay there, although the actual number is likely to have been higher. Given the collapse of the health system in Venezuela and low vaccination rates, migrants may have contracted infectious diseases before migrating or while travelling to Colombia.
The authors draw on monthly municipal data on the incidence of 15 infectious diseases between January 2012 and December 2018. They classify diseases into three categories: (i) vector-borne diseases, including malaria, dengue, leishmaniasis, chagas disease, and yellow fever; (ii) vaccine-preventable diseases, including chickenpox, measles, rubella, tuberculosis, diphtheria, and whooping cough (pertussis); and (iii) sexually transmitted diseases, including HIV, syphilis, hepatitis B, and chlamydia.
The authors exploit the fact that municipalities close to the main migrant arrival points experienced a disproportionate exposure to Venezuelan migrants. They estimate monthly migration inflows in each municipality based on the distance to the main migrant arrival points and the total monthly migration flows from Venezuela to Colombia. The authors also use the censuses of 1993, 2005, and 2018 to calculate a municipal measure of native out-migration to assess whether changes in the composition of the native population are driving the results.
- Higher inflows of Venezuelan migrants led to a higher incidence of vaccine-preventable diseases, including chickenpox and tuberculosis. When predicted migration inflows increased by one standard deviation, chickenpox and tuberculosis incidence increased by 0.22 and 0.23 cases per 100,000 individuals, respectively. These are sizable effects given that the mean incidence of chickenpox and tuberculosis during the period of study was 5.58 and 6.57 cases per 100,00 individuals, respectively. The effects of Venezuelan migration on the incidence of chickenpox are disproportionately concentrated in minors (individuals 18 years of age or less) and adults between 19 and 64 years of age. Tuberculosis is more prevalent in seniors (aged 65 or above).
- Higher inflows of Venezuelan migrants led to a higher incidence of sexually-transmitted diseases, namely syphilis and HIV for some regions. When predicted migration inflows increased by one standard deviation, the incidence of syphilis increased by 0.09 cases per 100,000 individuals. This is a substantial effect given that the mean incidence of syphilis during the period of study was 1.73 cases per 100,000 individuals. Syphilis is concentrated in adults (aged 19 to 64).
- There weren’t any significant effects of migration on the spread of vector-borne diseases.
- The Caribbean region was particularly affected by arrivals of Venezuelan migrants.
- Contact with infected migrants upon arrival seems to be the main mechanism driving increases in disease incidence. The spread of the diseases occurs five to six months after migrants arrive in Colombia and, in the case of chickenpox, in municipalities with incidence levels below the national mean before the onset of migration and in municipalities in which it was eradicated. Natives did not migrate from migrant hosting municipalities, so increases in the incidence of chickenpox, tuberculosis, and syphilis is not the result of changes in the composition of the population or the spread of disease due to internal migration.
The authors conclude that there are adverse effects of forced migration on the spread of chickenpox, tuberculosis and syphilis, driven by contact between recently arrived migrants and the local population. The authors recommend vaccination campaigns in regions with a high density of migrants and offering full health services to migrants on arrival. They note that providing access to health care may not be effective if it is not accompanied by regularization of migrants to ensure that they will not avoid using health services due to fear of deportation.