SECTION 4: RISK ASSESSMENT
Phase
Description
3
An animal or human-animal influenza reassortant virus has caused sporadic cases or small clusters of disease in people, but has not resulted in human-to-human transmission sufficient to sustain community-level breakouts. Human-to-human transmission of an animal or human-animal influenza reassortant virus able to sustain community-level breakouts has been verified. The same identified virus has caused sustained community-level outbreaks in two or more countries in one WHO region. In addition to the criteria defined in Phase 5, the same virus has caused sustained community-level outbreaks in at least one other country in another WHO region. Levels of pandemic influenza in most countries with adequate surveillance have dropped below peak levels. Levels of influenza activity have returned to levels seen for seasonal influenza in most countries with adequate surveillance.
4
5
6
Post-Peak Period
Post-Pandemic Period
Source: World Health Organization
HISTORICAL OCCURRENCES
INFLUENZA PANDEMICS Since the early 1900s, four lethal pandemics have swept the globe: Spanish Flu of 1918-1919; Asian Flu of 1957-1958; Hong Kong Flu of 1968-1969; and Swine Flu of 2009-2010. The Spanish Flu was the most severe pandemic in recent history. The number of deaths was estimated to be 50-100 million worldwide and 675,000 in the United States. Its primary victims were mostly young, healthy adults. The 1957 Asian Flu pandemic killed about 70,000 people in the United States, mostly the elderly and chronically ill. The 1968 Hong Kong Flu pandemic killed 34,000 Americans. The 2009 Swine Flu caused 12,469 deaths in the United States. These historic pandemics are further defined in the following paragraphs along with several “pandemic scares”. Spanish Flu (H1N1 virus) of 1918-1919 – In 1918, the Spanish Flu swept the world in three waves during a two-year period. The first reported case occurred at Camp Funston (Fort Riley), Kansas, where 60,000 soldiers trained to be deployed overseas. Within four months, the virus traversed the globe, as American soldiers brought the virus to Europe. The first wave sickened thousands of people and caused many deaths (46 died at Camp Funston), but it was considered mild compared to the second and deadliest wave, which struck in the autumn of 1918 and killed millions. At Camp Funston alone, there were 14,000 cases and 861 deaths reported during the first three weeks of October 1918. Outbreaks caused by a new variant exploded almost simultaneously in many locations including France, Sierra Leone, Boston, and New York City, where more than 20,000 people died that fall. The flu gained its name from Spain, which was one of the hardest hit countries. From there, the flu went through the Middle East and around the world, eventually returning to the United States along with the troops. Of the 57,000 Americans who died in World War I, 43,000 died from the Spanish Flu. At one point, more than 10 percent of the American workforce was bedridden. By a conservative estimate, a fifth of the world’s population suffered the fever and aches of influenza between 1918 and 1919 and 20 million people died. At the height of the flu outbreak during the winter of 1918-1919, at least 20% of North Carolinians were infected by the disease. Nearly 14,000 North Carolinians died from Spanish Flu. Asian Flu (H2N2 virus) of 1957-1958 – This influenza pandemic was first identified in February 1957. Unlike the Spanish Flu, the 1957 virus was quickly identified, and vaccine production began in May 1957. Several small outbreaks occurred in the United States during the summer of 1957, with infection rates highest among school children, young adults, and pregnant women; however, the elderly had the
Wake County, NC Multi-Jurisdictional Hazard Mitigation Plan
WSP June 2024 Page 176
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