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By Jacqueline Howard, CNN
4 minute read
Updated 11:37 AM EST, Mon January 21, 2019
This is an influenza virus particle, also known as a virion, according to the Centers for Disease Control and Prevention. Virions are made up of an outer protein shell and an inner core of nucleic acid: in this case, eight single-stranded RNA segments.
This illustration from the CDC is a 3-D graphical representation of an influenza virion's structure. Influenza viruses are members of the Orthomyxoviridae family, according to Encyclopedia Britannica, meaning their virions measure between 80 and 120 nanometers in diameter. Each virion contains hemagglutinin and neuraminidase antigens, substances that cause our bodies to produce antibodies. The amount of each antigen determines the strain of the virus, which is where the H#N# naming structure comes from.
This image depicts a number of influenza A virions. There are three basic types of influenza viruses -- A, B and C -- but only influenza A can infect animals, such as pigs or birds. When a virus strain enters an animal, it may change, causing a more serious epidemic when it returns to humans.
In 1997, scientists took lung tissue from five 1918 Spanish flu victims and extracted the nucleic acid to sequence the flu strain's genome. This image shows the re-created influenza virions that caused the outbreak, infecting close to a fifth of the world's population and killing an estimated 30 million to 50 million people in less than a year, according to the US Department of Health and Human Services.
These virions belong to the H3N2 flu virus that started in Hong Kong in 1968, according to the CDC. H3N2 infected an estimated 50 million Americans and killed 33,000 people in the United States, "making it the mildest flu pandemic in the 20th century," according to the Department of Health and Human Services.
Mexico and the United States first reported human cases of the H1N1, or swine flu, virus in April 2009, according to the World Health Organization. "Because there are human cases associated with an animal influenza virus, and because of the geographical spread of multiple community outbreaks, plus the somewhat unusual age groups affected, these events are of high concern," the WHO said at the time. The disease spread to more than 200 countries and has caused more than 18,000 deaths since 2009.
H1N1 was called "swine flu" because it was similar to the virus seen in pigs, as this photo illustrates. The WHO officially called an end to the H1N1 pandemic in August 2010, but cases with the strain still appear each year. "It is likely that the 2009 H1N1 virus will continue to spread for years to come, like a regular seasonal influenza virus," the CDC says.
In China in 2013, H7N9, or avian influenza A, was seen in poultry and in people who worked closely with poultry. In 2016, a number of provinces in China have shut down live poultry markets to prevent the spread of avian flu.
Flu under the microscope
CNN —
When it comes to vaccinating yourself – or your kids – against the flu, there are two options in the United States: a traditional shot or a nasal spray.
Yet among children, the nasal spray appeared to have reduced effectiveness against the flu, compared with the shot, in past flu seasons, according to a study published in the journal Pediatrics on Monday.
That finding, which involved analyzing data from several previous studies, seems to align with existing research.
“We were able to better describe vaccine effectiveness in age groups that the individual studies were not able to due to small sample sizes,” said Jessie Chung, first author of the study and an epidemiologist in the US Centers for Disease Control and Prevention’s Influenza Division.
The flu shot in the study is an inactivated influenza vaccine. The nasal spray, FluMist, is a live attenuated influenza vaccine. Though the viruses in FluMist are live, they have been weakened – attenuated, in medical terms – and work by stimulating the immune system.
MedImmune, a subsidiary of London-based AstraZeneca PLC, produces FluMist, which was approved by the US Food and Drug Administration in 2003.
Two of the new study’s 10 authors are employees of AstraZeneca, but Chung said the company was not directly involved in the study’s analysis.
For the 2018-19 flu season, which began in October, three types of vaccine are available in the United States: the inactivated influenza vaccine or IIV, administered as a shot; the recombinant influenza vaccine or RIV, also administered as a shot; and the live attenuated influenza vaccine or LAIV, administered as a nasal spray.
“CDC recommends annual influenza vaccination for everyone 6 months and older with any licensed, age-appropriate flu vaccine – IIV, RIV4 or LAIV4 – with no preference expressed for any one vaccine over another,” Chung said.
For the past two flu seasons, the CDC’s Advisory Committee on Immunization Practices, a panel of immunization experts, has not recommended the nasal spray. However, it was recommended again this flu season.
Dr. Pedro Piedra, a professor at Baylor College of Medicine in Houston, wrote an editorial accompanying the study in Pediatrics. He noted that the committee’s latest recommendation for the use of the nasal spray was based, in part, on new manufacturer data revealing improvements to performance. That new data was not included in the new study.
Meanwhile, the American Academy of Pediatrics recommends the inactivated flu shot as the primary choice for children “because it has provided the most consistent protection against all strains of the flu virus in recent years.”
The new study included data from five previously published studies on vaccine effectiveness during the 2013-14 and 2015-16 flu seasons. The data included 17,173 children, ages 2 to 17, from 42 states.
After combining data from all flu seasons, the researchers found that vaccine effectiveness against any type of flu virus was 51% for the inactivated flu shot vs. 26% for the nasal spray.
The study had some limitations, including that it relied on information provided in those previously published data.
“Despite combining data, we were still limited by sample size in some of our analyses,” Chung said. Additionally, more research is needed to determine whether similar findings would emerge in data from other flu seasons.
Some pediatricians, including Dr. Tanya Altmann, may prefer the nasal spray because that vaccine might not be as painful as a flu shot for their young patients. Of her three sons, Altmann said, two were given the FluMist this year, and one was given the shot.
“I’ve been practicing now for almost 20 years, and I did use the FluMist a lot when it was available, and I found that patients liked it because it wasn’t a shot – and, despite the study, I always felt like in my clinical practice it worked about as well as the shot,” said Altmann, founder of Calabasas Pediatrics Wellness Center in California and an American Academy of Pediatrics spokeswoman, who was not involved in the new study.
“The study did not include this current flu season, which from my understanding is a newly formulated FluMist vaccine. So the FluMist vaccine that I’m giving today in my office this season is different from the one that was studied. Only time will tell how effective the current FluMist vaccine is,” said Altmann, who is also author of the book “Baby and Toddler Basics.”
“I’m still hopeful,” she added. “I have no connection with the company. I just feel like it’s a good option, and I like the changes they made, and I want to give it another chance.”
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Regardless of the type of flu vaccine your family may prefer, Altmann said, what remains most important is getting vaccinated.
Nineteen states have high levels of flu activity, and 13 flu-related pediatric deaths have been reported during the current season so far, according to numbers the CDC released Friday.
While a flu vaccine is not 100% effective, it does lessen the severity of symptoms and the duration of illness in those who might get the flu.
“We know hands-down that getting any flu vaccine is better than getting no flu vaccine. So talk to your pediatrician or your doctor about what’s available this season,” Altmann said. “It’s not too late to still get a flu vaccine if you haven’t already because the flu is here. It’s everywhere, and it’s rapidly spreading and very contagious.”
CNN’s Susan Scutti contributed to this report.
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