A newly mutated influenza virus strain called H7N9 that could start a pandemic !

A new influenza virus strain was recently detected in China


The new H7N9 virus is a flu virus originating in birds called

avian influenza A(H7N9) virus.”


It is estimated that somewhere between 5% and 20% of U.S. residents get the flu in a typical year and more than 200,000 people are hospitalized with the flu every year according to the U.S. Centers for Disease Control and Prevention (CDC). Luckily the majority of persons infected with the influenza virus exhibit minor or few symptoms. Often the normal flu is self-limited, uncomplicated, and asymptomatic. Severe disease and complications due to infection, including hospitalization and death, can occur in elderly persons, in very young persons, in persons with underlying medical conditions, and in previously healthy persons.

Harper et al. in 2009 suggested that early treatment with antiviral medications may reduce the severity and duration of symptoms, hospitalizations, and complications. This could also reduce the use of outpatient services and antibiotics, extent and quantity of viral shedding, and possibly mortality in certain populations. Furthermore, vaccination is considered to be the best method for preventing influenza. The use of antiviral drugs may also prevent influenza transmission in certain settings.

The CDC Influenza Division estimated the range of deaths from between 151,700 and 575,400 people who perished worldwide from the 2009 H1N1 virus infection during the first year the virus circulated.

On Tuesday April 23, 2013 “theStar on line”  reports that the China bird flu has spread to new provinces and it was confirmed that the first case was identified in the eastern province of Shandong. The outbreak has killed 21 people so far. Since March 31 most cases have been confined to the commercial hub Shanghai and three nearby provinces, Jiangsu, Zhejiang and Anhui.

It is thought that presently a total number of 105 people are infected with the virus, according to official figures. The potential for the virus to mutate into a form easily transmissible between humans could then have the potential to trigger a pandemic. However, according to the World Health Organization (WHO) is still no evidence H7N9 was spreading in a “sustained” way between people in China. It is possible some family members may have infected one another.

As of April 18th 2013 a total of 87 laboratory confirmed human cases with avian influenza A(H7N9) virus including seventeen fatalities in China reported from four Provinces: Anhui 3 (1), Henan 3 (0), Jiangsu 21 (3) and Zhejiang 27 (2) and two Municipalities Beijing 1 (0) and Shanghai 32 (11) were reported by the CDC.

Spread of H7N9  EM of H7N9

Spread of the H7N9 virus.                                               Electron microscope image of influenza A H7N9 virus.

(Source: Science Volume 340 12 April 2013 page 130.           CDC website; http://www.cdc.gov/)

The World Health Organization (WHO) first reported 3 human infections with a new influenza A (H7N9) virus in China on April 1, 2013. Since then, additional cases have been reported. Most reported cases have severe respiratory illness and, in some cases, have died. No cases of H7N9 outside of China have been reported so far. Luckily the new H7N9 virus has not been detected in people or birds in the United States yet.

The new H7N9 virus is a flu virus originating in birds also called an “avian influenza virus.”  Human infections with avian influenza (AI, or “bird flu”) are rare but have occurred in the past. Infections occur most commonly after exposure to infected poultry. However, this is the first time that this bird flu subtype (H7N9) has been found in people. This virus is very different from other H7N9 viruses previously found in birds.

Since influenza viruses constantly change it is possible that this virus could gain the ability to become pandemic. Furthermore, there is no licensed vaccine for H7N9 available at this time. 

An update on human infection with avian influenza A(H7N9) virus in China can be found at


Investigations into the possible sources of infection and reservoirs of the virus are ongoing. Until the source of infection has been identified, it is expected that there will be further cases of human infection with the virus in China. So far, there is no evidence of ongoing human-to-human transmission. As of April 23rd 2013 WHO does not advise special screening at points of entry with regard to this event, nor does it recommend that any travel or trade restrictions be applied.

Naming of the virus

After broad consultations with experts from FAO, OIE and WHO, a consensus has been reached on the naming of the influenza A(H7N9) virus recently detected in China. The approach listed below was adopted and will be used in the three organizations’ communications.

• The core term is “avian influenza A(H7N9) virus“, which should be used for all scientific, technical or other reports.

• The core term can be further modified according to specific circumstances. For example:

o “human infection (or disease) caused by the avian influenza A(H7N9) virus”

o “chicken infection (or disease) caused by the avian influenza A(H7N9) virus”

o “swine infection (or disease) caused by the avian influenza A(H7N9) virus” – if detected in swine

 • For media communications, especially recognizing that social media such as twitter will gravitate towards use of shortest possible terms, it is suggested that terms such as “H7N9”, “H7N9 virus” be used as surrogates as needed.

The above joint standardization efforts from FAO, OIE and WHO are expected to streamline the communication at all levels globally.

The Influenza A Virus Genome

The influenza virus belongs to the Orthomyxoviridae family composed of six different RNA viruses. This virus is responsible for the common flu in birds, mammals, and humans.  The estimated death toll in the United States on average is 50,000 people annually. Symptoms usually include fever, headache, and nasal discharge which can develop into more obstructive pulmonary and heart problems including cardiac failure and bacterial pneumonia. The Influenza A virus genome is contained on eight single (non-paired) RNA strands that code for eleven proteins (HA, NA, NP, M1, M2, NS1, NEP, PA, PB1, PB1-F2, PB2). The total genome size is 13,588 bases. The segmented nature of the genome allows for the exchange of entire genes between different viral strains during cellular cohabitation. Hemagglutinin (HA) determines the extent of the infection of the host organism. During infection influenza viruses bud from the apical surface of polarized epithelial cells (e.g. bronchial epithelial cells) into the lumen of lungs. The infection primarily occurs in the lungs since HA is cleaved by tryptase clara which is restricted to lungs. Clara cells are dome-shaped cells with short microvilli found in the small airways (bronchioles) of the lungs. However HAs of H5 and H7 pantropic avian viruses subtypes can be cleaved by furin and subtilisin-type enzymes, allowing the virus to grow in other organs as well.

 H7N9 genome 1   H7N9 genome 2   H7N9 Nomenclature

 (Source: Science Volume 340 12 April 2013 page 129 – 130 and Wikepidia.)


The eight RNA segments of the viral genome


Encodes hemagglutinin

About 500 molecules of hemagglutinin are needed to make one virion



Encodes neuraminidase

About 100 molecules of neuraminidase are needed to make one virion



Encodes nucleoprotein

A protein that is structurally associated with nucleic acids



Encodes two matrix proteins (the M1 and the M2) by using different reading frames from the same RNA segment

About 3000 matrix protein molecules are needed to make one virion



Encodes two distinct non-structural proteins (NS1 and NEP) by using different reading frames from the same RNA segment



NS1 of influenza A is a 26,000 Dalton protein that prevents polyadenlylation of cellular mRNAs to circumvent antiviral responses of the host



Encodes an RNA polymerase

An enzyme that produces RNA



Encodes an RNA polymerase and PB1-F2 protein by using different reading frames from the same RNA segment

Targets the inner mitochondrial membrane via a amphipathic helix and disrupts mitochondrial function



Encodes an RNA polymerase

PB2  PB2 subunit of the RNA Polymerase affects virulence by interacting with the mitochondrial antiviral Signaling Protein and inhibiting expression of beta interferon


Monitoring the outbreak

The CDC is following this situation closely and is coordinating their efforts with domestic and international partners.  The CDC has issued guidance to U.S. clinicians and public health departments on how to test for this virus, interim guidance on case definitions for possible H7N9 cases in the United States, interim infection control guidance for U.S. health care workers and interim guidance on treating H7N9 with influenza antiviral drugs. CDC also has developed information for travelers to China.

General information about avian influenza viruses and how they spread is available at Avian Influenza A Virus Infections in Humans.



The CDS says “Take 3” Actions to fight the flu !

The flu is a serious contagious disease that can lead to hospitalization and even death.

The CDC urges you to take the following actions to protect yourself and others from influenza (the flu):

1.  Take time to get a flu vaccine.

CDC recommends a yearly flu vaccine as the first and most important step in protecting against flu viruses.

2.  Take everyday preventive actions to stop the spread of germs.:

  • Try to avoid close contact with sick people.
  • If you are sick with flu-like illness, CDC recommends that you stay home for at least 24 hours after your fever is gone except to get medical care or for other necessities. (Your fever should be gone without the use of a fever-reducing medicine.)
  • While sick, limit contact with others as much as possible to keep from infecting them.
  • Cover your nose and mouth with a tissue when you cough or sneeze. Throw the tissue in the trash after you use it.
  • Wash your hands often with soap and water. If soap and water are not available, use an alcohol-based hand rub.
  • Avoid touching your eyes, nose and mouth. Germs spread this way.
  • Clean and disinfect surfaces and objects that may be contaminated with germs like the flu.

3.   Take flu antiviral drugs if your doctor prescribes them.

  • If you get the flu, antiviral drugs can treat your illness.
  • Antiviral drugs are different from antibiotics. They are prescription medicines (pills, liquid or an inhaled powder) and are not available over-the-counter.
  • Antiviral drugs can make illness milder and shorten the time you are sick. They may also prevent serious flu complications.
  • Studies show that flu antiviral drugs work best for treatment when they are started within 2 days of getting sick, but starting them later can still be helpful, especially if the sick person has a high-risk health or is very sick from the flu. Follow your doctor’s instructions for taking this drug.
  • Flu-like symptoms include fever, cough, sore throat, runny or stuffy nose, body aches, headache, chills and fatigue. Some people also may have vomiting and diarrhea. People may be infected with the flu, and have respiratory symptoms without a fever.


Jon Cohen New Flu Virus in China Worries and Confuses. Science 12 April 2013: Vol. 340 no. 6129 pp. 129-130. DOI: 10.1126/science.340.6129.129.

Scott A. Harper, John S. Bradley, Janet A. Englund, Thomas M. File, Stefan Gravenstein, Frederick G. Hayden, Allison J. McGeer, Kathleen; Seasonal Influenza in Adults and Children-Diagnosis, Treatment, Chemoprophylaxis, and Institutional Outbreak Management: Clinical Practice Guidelines of the Infectious Diseases. Society of America. Clin Infect Dis. (2009) 48 (8): 1003-1032. doi: 10.1086/598513

Categories: Bioanalysis, DNA, Flu, H1N1, H7N9, Synthesis, Vaccines, Virus

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