South Korean officials have said that the disease, only referred to be North Korea as an "acute enteric epidemic" is likely to be either cholera or typhoid.
The launch came a week after South Korea and the United States fired eight surface-to-surface missiles in response to North Korea firing eight short-range ballistic missiles toward the East Sea.
North Korea has carried out at least 18 rounds of weapons tests this year, underscoring its evolving nuclear and missile arsenals.
The South Korean and US militaries fired eight surface-to-surface missiles on Monday.
The missiles were fired from the Sunan area of the North Korean capital Pyongyang, South Korea's Joint Chiefs of Staff said.
This year, North Korea has tested a flurry of ballistic missiles that are banned by the United Nations Security Council Resolutions.
On several occasions from April 26 to May 26, Chinese aircraft approached a Royal Canadian Air Force long-range patrol aircraft, forcing it to divert from its flight path.
It's “absurd” that the government has not been able to decide what to do about the settlement of Homesh, he said.
China and Russia vetoed a US-led push this week to impose more United Nations sanctions on North Korea over its ballistic missile launches.
Two weeks ago state media revealed the outbreak, fueling concerns about a lack of vaccines, medical supplies and food shortages