August 2, 2018

One hundred years ago, in 1918, the Spanish flu began taking its deadly toll around the world. The Spanish flu was the worst outbreak of influenza, or flu, in history. Medical historians estimate that from 1918 through 1919, the Spanish flu killed at least 600,000 people in the United States and 20 million to 50 million people worldwide. The Spanish flu was the first and most severe of three pandemics (worldwide occurrences) of influenza in the 1900’s. Less severe pandemics occurred in 1957 and in 1968.

The Camp Jackson Base Hospital in South Carolina is filled with Spanish flu patients in the fall of 1918. Credit: Otis Historical Archives/National Museum of Health and Medicine

The Spanish flu struck in the final year of World War I (1914-1918), while many European nations were concentrating on war efforts. Many soldiers died of influenza, and troop concentrations and movements helped spread the disease. Most countries at war did not publicly acknowledge the number of deaths from influenza because of strict wartime censorship. The pandemic became known as the Spanish flu because the disease was widely reported in Spain, which remained neutral during the war.

Spanish flu caused symptoms similar to other influenza infections, including fever, chills, headaches, body aches, and fatigue. However, many people suffering from Spanish flu quickly developed severe pneumonia (inflammation of the lungs) and pulmonary edema (excess fluid accumulation in the lungs), causing victims to suffocate. Unlike other varieties of influenza, which most seriously affect infants and the elderly, the Spanish flu killed mainly young, healthy adults between 20 and about 40 years of age.

Medical historians believe the virus that caused Spanish flu, like many strains of influenza virus, probably originated in Asia. However, the first reported outbreaks of the disease occurred in the United States. The disease quickly spread to Europe, Asia, Africa, and South America. During the height of the pandemic, the huge number of deaths severely disrupted many societies. Many countries tried various public health measures to contain the pandemic. In the United States, several cities closed schools, churches, theaters, and other public gathering places. By the end of 1919, the pandemic had largely ended.

Scientists have long sought to discover why the particular variety of influenza that caused the Spanish flu was so deadly and spread so quickly. In the 1990’s, they identified preserved lung tissue of victims of the disease that still contained the genetic information from the Spanish flu virus. They confirmed it as a variety of H1N1, one of several types of influenza viruses that can infect both people and certain animals, such as swine. Scientists believe birds are the original source of the Spanish flu and other pandemic influenza viruses. Birds carry many varieties of influenza viruses and in rare occasions transmit these viruses to human beings. In 2005, scientists re-created the Spanish flu virus through a process called reverse genetics. By studying the virus, they hope to discover why the disease spread so quickly and why it was so deadly. In addition, scientists can study the Spanish flu virus to develop new vaccines and treatments to prevent or contain future influenza outbreaks.

December 5, 2014

Officials at the United States Centers for Disease Control and Prevention (CDC) are finding that vaccines administered this year to protect people from influenza (the flu) are not as effective as they had hoped. But, they stressed, people should not use this as an excuse to skip this year’s flu shot. In addition to feeling miserable, people with the flu may develop flu-related complications that may lead to hospitalization and death, health officials said. Children and the elderly are especially at risk.

Global flu outbreaks occur each year, usually in winter months. Each outbreak is caused by viruses slightly different from those associated with earlier outbreaks. The differences are caused by mutations that occur in the viruses. A mutation is a change in the hereditary material of an organism. Mutations in a flu virus may cause an unexpected flu strain to become more common in a given year. That seems to be the case in 2014. This strain was associated with severe outbreaks, including higher-than-normal numbers of hospitalizations and deaths, during the 2003-2004, 2007-2008, and 2012-2013 flu seasons.

Influenza viruses may cause flu when they are inhaled. The viruses shown here are greatly magnified and artificially colored. (© Linda Stannard, UCT/SPL from Photo Researchers)

Vaccine manufacturers must produce flu vaccine months before any outbreak in order to ensure sufficient vaccine supplies when flu season hits. But the vaccine must closely match the strains (types) in each year’s outbreak. The decision on what strains should be used in a year’s vaccine is based on the common strains found worldwide by global health agencies in the past year. However, CDC scientists found that fewer than half of the flu virus samples obtained from patients from October and November 2014 matched any of the strains used to make this year’s vaccines. Scientists often name the different flu strains after the place where the strain was first identified. This year’s flu vaccines were made to match several flu strains, including one called A/Texas/50/2012. But in samples from flu patients taken in October and November, only 48 percent matched this flu strain. Most of the other virus samples were from a strain called A/Switzerland/9715293. This strain was not used to make flu vaccine in 2014. As a result, the flu vaccine currently used is not as effective at protecting people from this strain.

Nevertheless, medical experts note that even if a vaccine does not exactly match the most common strains of flu circulating, the vaccine still provides significant protection. People who have had a flu shot may still get sick this year. However, they will typically experience a less severe illness than they would have without the shot. CDC officials stressed that over the years, hundreds of millions of Americans have safely received flu vaccines. The most common side effects are soreness, redness, tenderness or swelling where the flu shot was given and nasal congestion after the flu vaccine nasal spray.

Additional World Book articles:

• Epidemic
• Spanish flu
• Influenza: A New Threat from an Old Foe (a Special Report)
• Handwashing: The First Line of Defense Against Disease (a Special Report)

Information about flu and flu vaccines can be found on the Influenza page of the CDC website.

June 16, 2014

In a series of controversial experiments, scientists at the University of Wisconsin in Madison have re-created in a laboratory a strain of influenza virus that closely resembles the virus responsible for the Spanish flu pandemic (global occurrence) of 1918 that killed over 50 million people worldwide. The scientists contend that they re-created the deadly virus as a necessary step to help combat future flu pandemics. However, critics of the research argued that the experiments should be halted immediately as they pose a great threat to public safety.

Influenza tends to occur in widespread epidemics that occur most every year. Each outbreak is caused by a virus slightly different from earlier ones. Some strains (types) cause mild or moderate illness, and others cause many deaths. The Spanish flu of 1918 was the deadliest outbreak of influenza in history. Medical historians believe the Spanish flu virus, like many strains of influenza, probably originated in Asia. The disease quickly spread to the United States, Europe, Africa, and South America. During the height of the pandemic, the huge number of deaths severely disrupted many societies. Less severe pandemics occurred in 1957 and in 1968 but still resulted in many deaths.

Influenza viruses (shown here are greatly magnified and artificially colored) may cause flu when they are inhaled. (© Linda Stannard, UCT/SPL from Photo Researchers)

The Wisconsin scientists, led by Yoshihiro Kawaoka, isolated several genes from influenza viruses that normally infect wild ducks in Asia. These “avian influenza” (also known as “bird flu) viruses often mutate so they can infect mammals, including humans, and spread in global pandemics. Using a technique known as “reverse genetics,” the scientists used the individual genes to reconstruct an entire flu virus. They compared this rebuilt virus to virus samples from frozen corpses of victims of the 1918 Spanish flu pandemic recovered in Alaska. The rebuilt virus was 97 percent identical to the deadly Spanish flu virus.

The scientists infected ferrets with the re-created virus so they could study how it infected and spread among mammals. Kawaoka contends that such experiments are important so scientists can understand why the 1918 Spanish flu virus was so lethal, compared to other strains of flu that originate in wild birds. For example, the scientists identified a mutation in the rebuilt virus that enabled it to spread more easily from one animal to another. Scientists argue that continued research will help them better understand how the virus infects animals and makes them ill. This information will be useful for developing effective vaccines and treatments to combat future flu pandemics.

Other scientists argue that the research is too dangerous to continue and that another Spanish flu pandemic is unlikely to occur naturally. They claim that the most serious risk lies with the rebuilt virus being released from the high-security laboratory through some accident. Should an infected research animal escape, the deadly virus could spread rapidly in a new global pandemic with catastrophic results. The United States National Institutes of Health (NIH) which funds the controversial research, insisted that proper safety measures are being taken and that funding for the research would continue.

Additional World Book articles:

• SARS
• Swine flu
• Influenza: A New Threat from an Old Foe (a Special Report)
• Medicine in the 21st Century: The Promise of Genetics (a Special Report)

January 11, 2013

Three separate flu or flu-like epidemics are emerging simultaneously across North America. The first includes an unusually aggressive flu virus that is showing up earlier than usual. The second is a surge of cases from a new type of norovirus. The third is a whooping cough outbreak, the worst in 60 years.

Forty-seven states reported that the flu had become widespread during the week ending January 5, up from 41 states the previous week, the Centers for Disease Control and Prevention (CDC) announced today. The most common strain currently moving across the county is an H3N2. This strain is more lethal than H1N1, the strain that typically appears in the United States at this time of year. The number of flu cases is currently “elevated” across the United States, except in Arizona, California, Hawaii, and Nevada. However, 24 states and New York City have reported “high levels” of flu-like illness to the CDC. On January 9, the mayor of Boston declared a public health emergency because of the number of flu cases flooding the city’s hospital emergency rooms. Across the United States, more than 3,700 people, primarily senior citizens, have been hospitalized with the flu and at least 20 children have died from the H3N2 strain since the season began this fall.

Cities across Canada have reported outbreaks of norovirus so serious that hospitals are shutting down and disinfecting whole wards because patients were becoming infected after checking in with a different ailment. The new strain is known as the Sydney 2012 variant, because it first appeared in Australia. The classic symptoms are “explosive” diarrhea and “projectile” vomiting.

Flu is caused by a virus, such as the ones above, which have been greatly enlarged and artificially colored. (© Linda Stannard, UCT/SPL from Photo Researchers)

In early January, the CDC reported 42,000 confirmed cases of whopping cough in the United States in 2012, the biggest outbreak in  60 years. The disease is unrelated to flu but causes a hacking, constant cough and breathlessness. Infants, especially premature infants, are at greatest risk. There were 18 recorded deaths from whopping cough in the United States in 2012.

The CDC and the local health authorities strongly advocate getting flu shots. Based on data from some 1,155 children and adults with acute respiratory infections, flu vaccines are judged to be 62-percent effective. William Schaffner, chairman of the department of preventive medicine at Vanderbilt University in Nashville, Tennessee, has characterized this level of effectiveness as “normal.” “It’s a good but not a perfect vaccine,” he noted.

Additional World Book articles:

• Spanish flu
• Swine Flu
• Disease Detectives (a special report)
• Influenza: A New Threat from an Old Foe (a special report)
• Public health 2009 (a Back in Time article)