An infectious agent appears most likely, especially as siege camps were notorious for poor sanitation and polluted water supplies.

One possibility is a virus. In 1918 an influenza epidemic caused 20 million deaths world-wide, almost more than the number of fatalities in World War I. Viral haemorrhagic fevers such as Ebola can also spread rapidly and are frequently fatal. Herodotus (c.488-428 BC), the Greek historian, attributed the deaths to bubonic plague, the same disease that wiped out one third of Europe's population in the 14th Century. Yersinia pestis is carried by flea-infested rats and the conditions of a siege camp would be perfect for its spread.

However, neither plague nor viral illnesses are likely to have caused the vast majority of fatalities on the same night.

Luke, therefore, favours a diagnosis of cholera which can incubate in only a few hours before causing prostration and death unless swiftly treated. The fact that all the deaths occurred at the same time could be explained by the water supply becoming contaminated so that each soldier received a fatal load of Vibrio cholereae in his daily ration.

Whatever the cause we can be sure that it was God who delivered Jerusalem from her attackers (Isaiah 37:36). The death of the 185,000 coupled with the news of the Cushite King's approach (Isaiah 37:9) forced the Assyrians to lift their siege of Jerusalem, fulfilling Isaiah's prophecy (Isaiah 37:33-35). Hezekiah, the King of Judah, was tempted to surrender (Isaiah 36:4-22) but chose instead to trust in the Lord and resist the assault (Isaiah 37:14-20).

The story gives us a great example to follow as well as showing the reality of God's sovereign rule over all things.