Table 1.

Common reasons for an increase in infectious diseases during conflict

Causes of an increase in infectious disease	Mechanisms of action	Examples
Increased burden of disease	Migration leads to the migration of infectious diseases infecting new non-immune hosts.	The United Nations High Commissioner for Refugees (UNHCR) estimates that there are 15.3 million refugees and a further 26 million internally displaced persons (IDPs) worldwide [116]. Migration in camps that are overcrowded leads to situations where sanitation is not adequate and outbreaks can occur [117], a consideration going back nearly a century to the start of World War II [118].
	Breakdown of prevention programs leading to an increase in vector-borne diseases, such as malaria and trypanosomiasis.	Afghanistan has seen an increase in malaria after it had successfully controlled this disease in the 1970s and the Democratic Republic of Congo has had a rise in trypanosomiasis in conjunction with the rise in conflict [119]. Refugee camps in Sierra Leone and Guinea have both seen outbreaks of Lassa fever from the infestation of rodents [120,121].
Susceptibility of the population to infectious diseases	Reduced immunity from malnutrition, inadequate coverage of immunizations and the loss of herd immunity and the lack of innate immunity to unseen infective organisms.	Afghan refugees from a malaria-free region who fled to Pakistan in 1981 had a prevalence of malaria more than double that of the local population, and a ten-fold increase in burden over the following decade [122].
Breakdown of the healthcare system	Healthcare may be suspended or diminished [2] and funds diverted from it to armed forces or security actors. This leads to reduced detection and treatment of infectious diseases and potentially to increased rates of antibiotic resistance. This is combined with difficulties in accessing the services that do function due to fear of movement or breakdown of the transport networks.	The restriction of transport networks by the Maoist rebels in Nepal in 2005 held up the supply of vaccines, vitamin A, and deworming drugs to nearly 3.6 million Nepalese children [123].
		Even normally functioning immunization programs can be affected by security concerns, the polio eradication program in Afghanistan being an example [124]. During the conflict in Bosnia and Herzegovina in the early 1990s, immunization rates fell from approximately 95% pre-conflict to around 30% [125]. Health facilities may themselves come under deliberate attack [8][124,126]. In the Nicaraguan conflict of the mid-1980s, approximately a quarter of the health facilities were partially or completely destroyed [54].
	Movement of healthcare workers	Healthcare workers often have the socioeconomic wherewithal to migrate during conflicts. A report from the International Committee of the Red Cross quotes an Iraqi Ministry of Health estimate that 18,000 of the country’s 34,000 doctors left [127]. Liberia is thought to have seen a decrease from 237 to 20 doctors during recent conflict [128].