요약

The previous chapter considered how short-term variations in climatic conditions

and extreme weather events can exert direct effects on human death rates, physical

injury, mental health and other health outcomes. Changes in mean climatic

conditions and climate variability also can affect human health via indirect pathways,

particularly via changes in biological and ecological processes that influence

infectious disease transmission and food yields. This chapter examines the

influences of climatic factors on infectious diseases.

For centuries humans have known that climatic conditions affect epidemic

infections—ince well before the basic notion of infectious agents was understood

late in the nineteenth century. The Roman aristocracy took refuge in their

hill resorts each summer to avoid malaria. South Asians learnt early that in high

summer, strongly curried foods were less prone to induce diarrhoeal diseases.

In the southern United States one of the most severe summertime outbreaks of

yellow fever (viral disease transmitted by the Aedes aegypti mosquito) occurred in

1878, during one of the strongest El Niño episodes on record. The economic and

human cost was enormous, with an estimated death toll of around 20 000 people.

In developed countries today it is well known that recurrent influenza epidemics

occur in mid-winter.

Infectious disease transmission should be viewed within an ecological framework.

Infectious agents obtain the necessary nutrients and energy by parasitization

of higher organisms. Most such infections are benign, and some are even

beneficial to both host and microbe. Only a minority of infections that adversely

affect the host’ biology are termed “nfectious disease”