Scientists Uncover Mystery of Flu Virus Evolution

Researchers at the University of Rochester Medical Center (URMC) have uncovered the mechanism that lets the flu virus evolve so efficiently within and between host species. In their research, the scientists found that the secret to the flu virus’s evolutionary success lies in its unique replication process. Previously, scientists thought that the flu virus evolved so quickly due to an error-prone replication process. However, this new research refutes that hypothesis. Instead, the researchers discovered that the flu virus’s unique replication process lets enough mutations form that the virus can easily spread and adapt to its host environment. In addition, this replication process allows just enough mutations to occur without causing catastrophic mutagenesis—that is, without killing itself in the process.

These new findings give us insights into how we may be able to control viral evolution,” Baek Kim, Ph.D., professor in the department of Microbiology and Immunology at UMRC and lead study author, said in a press release about the discovery. This research presents an attractive strategy for tackling the flu—making the influenza virus kill itself by amplifying the number of mutations made beyond the desired level, which is lethal for the virus.

In their study of the mechanisms behind flu virus evolution, the researchers used biochemical analysis methods to compare flu virus replication with human-immunodeficiency virus (HIV) replication. The scientists found that while the polymerases, that is, the enzymes, behind replication are quite error-prone in HIV, they are much more accurate in the flu virus. Though both viruses depend on mutations for survival, HIV is only able to replicate its genome a few times during an infection, meaning it isn’t able to produce that many mutations. In contrast, the flu virus replicates itself a number of times during an infection, and this gives it ample time to produce a huge number of mutations that allow the virus to thrive.

The results of the scientists’ research was published online in the April 29, 2010 edition of the open-access journal PLoS One. Researchers who contributed to this study included Shilpa Aggarwal, Birgit Bradel-Tretheway, Toru Takimoto, Stephen Dewhurst, and Baek Kim.

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WHO Declares H1N1 Flu Virus Outbreak a Pandemic

On June 11, 2009, the World Health Organization raised the alert level to phase 6meaning that the occurrence of swine flu can be categorized as a pandemic. Since the virus was first identified, over 30,000 cases of swine flu have been diagnosed in North America, Europe, Australia, South America, and other locations across the globe. The WHO opted to change the alert level due to the global spread of the flu virus, and not because of the severity of the virus. Thus far, most cases of the H1N1 flu virus in the United States have been mild, and most people infected by the virus have recovered without requiring professional medical treatment. However, because the H1N1 flu virus is a new virus, most people have little to no immunity against it. Health officials worry that the severity of the H1N1 flu virus could increase over time, especially during the fall and winter when the flu season hits. This is especially worrisome given the current lack of a vaccine against the virus.

Cases of the H1N1 flu virus were first detected in Mexico, and have since spread into the United States and worldwide. The first confirmed case of the H1N1 flu virus in the United States was identified on April 15, 2009. Since the outbreak began, cases have been identified in all 50 states. Early outbreaks around the globe centered on travelers who had recently returned from trips to Mexico. Currently, countries in the Southern Hemisphere, including Australia and New Zealand, are experiencing an rise in the number of H1N1 flu virus infections; that part of the world is just entering the influenza season.

Of the 30,000 reported cases of H1N1 flu virus infection, there have only been 144 deaths. To put this in perspective, according to data presented by the Centers for Disease Control (CDC), every year in the United States, about five to 20 percent of the population comes down with a case of the seasonal flu, and about 36,000 Americans die every year from flu-related complications.

Following are a few answers to some questions you may have about the H1N1 flu virus.

What is the H1N1 virus?

The influenza A(H1N1) virus is a new type of flu that was first detected in the United States in April 2009.

The H1N1 flu virus. (Photo credit: CDC Influenza Laboratory)

Why was it called the swine flu?

The H1N1 virus was originally referred to as the “swine flu” because initial testing showed that the virus carried a number of genes similar to flu viruses that typically occur in North American pigs. Further testing showed that the virus is actually a quadruple reassortment virus that contains two genes that normally infect European and Asian pigs along with a gene from humans and a gene from birds.

What are the symptoms of the H1N1 virus?

Symptoms of the H1N1 flu virus are similar to the symptoms of the seasonal flu. These symptoms include fever, body aches, headache, chills, cough, sore throat, and fatigue. In some cases, occurrences of diarrhea and vomiting have also been reported. Although cases in the United States have generally been mild, some populations of people may be more susceptible to the virus, including the very young the very old, pregnant women, and those with chronic conditions or compromised immune systems.

How is the virus spread?

The virus is spread by human-to-human contact through coughing, sneezing, or touching something infected by the virus and then touching one’s eyes, nose, or mouth. You cannot contract the H1N1 virus by eating cooked pork or pork products.

What are ways to prevent illness?

Wash your hands frequently with soap and water. Alcohol-based hand sanitizers can also be used to protect yourself from flu germs. Use a tissue to cover your mouth when you cough or sneeze and throw the tissue away after it’s used. If you have symptoms of the flu, stay at home. If at all possible, limit your contact with those you know to be infected with the H1N1 flu.

Is there a vaccine for the H1N1 virus?

There is not currently a vaccine for the H1N1 virus, though scientists are at work developing one. There are several antiviral medications that are recommend for use for those who have the H1N1 virus such as oseltamivir and zanamavir. These medications help prevent the flu virus from reproducing in your body and make flu symptoms milder. However, in many cases getting plenty of rest and drinking plenty of fluids is all that is necessary to get over a case of the H1N1 flu.

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