Optimizing Barrier Protection During a
Pandemic Event Caused by Influenza A

Pandemics of Influenza A Over the Last Century See Table 1 below for a summary of the pandemic events occurring during the last century. 1918-1919 SPANISH FLU A pandemic of the Spanish influenza, type A (H1N1), in 1918-19 caused the highest number of known deaths from influenza. The Spanish Flu epidemic did not originate in Spain; it was first reported in Europe and in certain states in the U.S. in February 1918. The second wave began almost concurrently in France, Sierra Leone, and the entire U.S. The second wave saw a tenfold increase in the death rate. The disease had characteristics that were not witnessed before and, luckily, have not been seen since. One of the most unusual aspects of the Spanish Flu was its ability to kill young adults, and it is unknown why this occurred. The usual high-risk group for influenza includes the very young and the very old or the already immunocompromised population. During the Spanish Flu, mortality rates were high among healthy adults as well as the usual highrisk groups. The attack rate and mortality were highest among adults 20 to 50 years old.5 Victims could feel ill in the morning, become very sick by noon, and be dead by nightfall. Others died of complications soon after. Nearly half of those who died were young, healthy adults. Approximately 99% of the deaths were among people under the age of 65.5,6 Antibiotics had not yet been discovered and secondary complications, such as bacterial pneumonia, killed the majority of the victims. Viral pneumonia also occurred, causing the lungs to hemorrhage. This situation could kill a perfectly healthy young adult within 48 hours.6 The first vaccine for influenza was not developed until 1933, so the only defenses available to health officials were isolation and quarantine. Schools and public institutions were closed and public gatherings were banned. In some countries, people would wear gauze masks in public. In other areas, it was against the law to have an unprotected cough or sneeze in public; if you were caught doing so, you were fined or jailed.6 With the exception of Australia, the majority of isolation and quarantine techniques around the world did not work. Australia maintained a strict maritime quarantine, staving off arrival of the epidemic until the start of 1919. By that time, the virus was not as destructive and Australia experienced a milder, although longer, period of influenza activity than anywhere else. However, the virus continued to affect the young and healthy with 60% of deaths occurring in persons aged 20 to 45 years.7 Over the course of the pandemic, an estimated 25 - 30% of the world population fell ill. Hospitals, medical supplies, morgues, mortuaries, and mortuary supplies (coffins and burial space) could not keep up with the pace of the spread of the disease and the rate of death. No area of the world was spared. Globally, the demographic effect was enormous; in some areas, life expectancy dropped by 10+ years.8 1957-1958 ASIAN FLU In 1957, there was a pandemic of a much milder form than that of 1918; still, the global death toll was estimated to be around 2 million. It was first identified in Guizhou or Yunnan province in southwestern China in late February 1957. Within six months, most areas of the world were battling what became known as Asian Flu. The Asian Flu is influenza A (H1N2). This flu caused about 70,000 deaths in the United States and an estimated 10 - 35% of the world’s population was affected.9 During the 1957-1958 pandemic, a World Health Organization (WHO) expert panel found that the spread of the virus within some countries followed public gatherings. This panel also observed that in many countries the pandemic broke out first in schools, camps, and army units. The suggestion by this expert panel was that the avoidance of crowds might contribute to a decrease in the peak incidence of an epidemic.10 The virus came to the U.S. quietly with a series of small outbreaks over the summer of 1957. Children started spreading the virus at home when school started in the fall season of 1957. A published study found that during an influenza outbreak, school closures were associated with significant decreases in the incidence of viral respiratory diseases and healthcare utilization among children aged 6-12 years.11 During October 1957, infection rates were highest among school children, young adults, and pregnant women. In January and February 1958, there was another wave of influenza among the elderly. This is an instance of the potential “second wave” of infections that can arise during a pandemic. The disease infects one group of people first, infections appear to decrease, and then infections increase in a different part of the population. Even though fewer of the elderly acquired the disease, they had the highest influenza-related death rate during this time.12 Unlike the 1918 pandemic, the 1957 pandemic virus was quickly identified due to technological and scientific advancements. Vaccine production for the Asian Flu began about three months after the first outbreaks occurred in China. Vaccine was available in limited supply by August 1957, and by mid-October—at the peak of the U.S. pandemic—fewer than half of the approximately 60 million doses produced had been delivered. TABLE 1. THE LAST CENTURY’S PANDEMICS* YEAR 1918-1919 1957-1958 1968-1969 Influenza type Spanish Flu Asian Flu Hong Kong Flu Estimated global deaths 50 million 1 million 1 million Estimated deaths in the U.S. 500,000 70,000 34,000 Suspected origination of the influenza type First heard of in particular states in the U.S. and in Europe China China Age group most affected Healthy young adults (age 20-50) The very young and the very old The very old and those with underlying medical conditions Vaccine made available No vaccinations available. Vaccinations made available six months after the first case of influenza was noted. Vaccinations made available one month after the first case of influenza was noted. *Information obtained from WHO and Centers for Disease Control and Prevention (CDC) websites THE PANDEMIC OF 1968-1969 The most recent influenza pandemic occurred in 1968 with the Hong Kong Flu (H3N2) outbreak, which resulted in nearly 34,000 deaths in the United States. The 1968-69 pandemic, which was milder than the pandemic of 1957, is thought to have caused approximately 1 million deaths worldwide. In early 1968, the Hong Kong influenza pandemic was first detected in Hong Kong. It spread worldwide during the following two winters, causing greater morbidity in some countries than the first winter and in other countries during the second winter. The first cases in the U.S. were detected as early as September 1968, but the illness did not become widespread in the U.S. until December 1968. Deaths from this virus peaked in December 1968 and January 1969. Those over the age of 65 were most likely to die. The same virus returned a year later, in late 1969 and early 1970 (peaking in the U.K. in January 1970), and in 1972. In the 1968 pandemic, vaccine became available one month after the outbreaks peaked in the U.S.13 The variant was first isolated and identified in Hong Kong in July 1968. Within a few months, cases of the Hong Kong Flu appeared around the world. Hardest hit by the pandemic were children under age 5 and adults ages 45 to 64. In the United States, an estimated 30 million people were infected and there were some 33,000 influenza-related deaths.14 There are several potential reasons fewer people in the U.S. died as a result of this virus: The Hong Kong Flu virus was similar in some ways to the Asian Flu virus that circulated between 1957 and 1968. Earlier infections by the Asian Flu virus might have provided some immunity against the Hong Kong Flu virus, which may have helped to reduce the severity of illness during the Hong Kong pandemic. Rather than peaking in September or October like pandemic influenza had in the previous two pandemics, this pandemic did not gain momentum until near the school holidays in December. Since children were at home and did not infect one another at school, the rate of influenza illness among children in school and their families declined. Improved medical care and antibiotics that were more effective for secondary bacterial infections were available for those who became ill. AVIAN FLU (THE BIRD FLU) During 2004, large parts of Asia experienced unprecedented outbreaks of highly pathogenic Avian influenza caused by the H5N1 virus in poultry. At the same time, health officials were swift to restore confidence with the public that the H5N1 virus, deadly to birds, was incapable of infecting humans on an extensive scale, and that few, if any, cases of human-tohuman transmission of the virus had occurred. Multiple countries were conscious of the negative economic impact this could have on the poultry industry, so they quickly reassured the public that eating poultry was safe. The Avian Flu was formerly known as the “fowl plague.” Avian influenza A (H5N1) infections occurred in both poultry and humans, and marked the first time an Avian influenza virus had ever been found to transmit directly from birds to humans. During this outbreak, 18 people were hospitalized and 6 died. To control the outbreak, authorities killed about 1.5 million chickens to remove the source of the virus. Scientists determined that the virus spread primarily from birds to humans, although rare person-to-person infection was noted. The virus crossed the species barrier to infect humans with a high rate of mortality. Monitoring of the evolving situation, coordinated by WHO, has revealed many signs that a pandemic may be imminent. FACTS ABOUT AVIAN INFLUENZA Avian Flu is a disease that affects birds, and is caused by different strains of the Type-A influenza virus. The disease is infectious as it spreads easily between birds. The H5N1 virus has been identified in birds throughout Asia, and in European countries including Romania, Bulgaria, Croatia, and Germany. Of the 16 types of Avian Flu, H5N1 is the type health experts are most concerned about. “H” and “N” refer to proteins on the surface of the virus; “5” and “1” refer to different forms of the proteins. H5N1 has pandemic potential because it may eventually alter into a form that is contagious in humans. Most Avian Flu viruses only infect birds and pigs. However, this flu has also been identified in humans, horses, tigers, birds, and certain marine animals. The virus subtypes that cause birds to fall ill do not contain the “keys” needed to infect humans. Infected birds can spread the virus through saliva, nasal secretions, and feces. If an infected bird survives, it excretes the virus for 10 days after other signs of illness subside. In 1997, health officials in Hong Kong documented 18 cases of infection in humans by a subtype of Avian influenza virus known as H5N1.16 Of the 18 people infected, 6 died. As of December 31, 2005, the H5N1 virus had infected 284 people, 148 of whom died, and 2 of those deaths were a result of human-to-human contact.17 See Table 2 below for a summary of confirmed human cases of Avian influenza. Health officials are concerned that the Avian influenza virus (H5N1) may “swap” genetic information with the human flu virus and develop the ability to infect people easily, leading to an influenza pandemic. Currently, the H5N1 virus has developed a limited ability to infect humans. Human-to-human transmission of the H5N1 virus is extremely rare and has been reported in only a few families. Health officials are working to control the spread of the H5N1 virus by slaughtering infected birds, placing limits on bird importation, and carefully tracking reported cases of both bird and human infection. Some antiviral medications may be effective in preventing and treating Avian influenza. However, the H5N1 virus has already developed resistance to two commonly used antiviral medications. The survival time of the H5N1 virus varies widely and is dependent upon temperature, humidity, and other conditions. The virus may survive for weeks in cool, moist conditions. In this way, the virus can spread from farm to market, from farm to farm, or from farm to a poultry worker’s home. In its most lethal forms, Avian influenza begins suddenly, causes severe illness, and quickly leads to death in almost all infected birds. This form is referred to as “highly pathogenic Avian influenza.” Highly pathogenic Avian influenza causes severe epidemics of disease. In October 2005, health officials confirmed that birds infected with bird flu had been identified in Turkey and Romania, showing that the deadly bird flu virus had reached Eastern Europe. In the United Kingdom, veterinarians confirmed that an imported parrot, still in quarantine, was infected with a highly pathogenic strain of H5 Avian influenza. The bird was destroyed, as were other birds it may have infected. TABLE 2. CUMULATIVE NUMBER OF CONFIRMED HUMAN CASES OF AVIAN INFLUENZA A/(H5N1) REPORTED TO WHO* Country 2003 2004 2005 2006 2007 Total   Cases Deaths Cases Deaths Cases Deaths Cases Deaths Cases Deaths Cases Deaths Azerbaijan 0 0 0 0 0 0 8 5 0 0 8 5 Cambodia 0 0 0 0 4 4 2 2 1 1 7 7 China 1 1 0 0 8 5 13 8