Influenza A (H7N9) influenza virus subtype New Influenza A (H7N9) producer of serious infections in people in China, with possible pandemic potential

Information 05/13/13.

There have been cases of infection with influenza virus H7 subtypes (H7N2, H7N3, H7N7), which have affected people with cases or outbreaks described in Holland, Italy, Canada, USA, Mexico, and the United Kingdom, most often related to outbreaks affecting poultry. In people they have caused conjunctivitis, or mild upper respiratory infections, except the death of a veterinarian in the Netherlands.

Recently, in February 2013, began to describe cases in China, a new subtype of influenza A virus (H7N9), unlike what happened with other subtypes of Influenza A H7 virus is causing a progressive increase in the number of cases and also with a higher gravity has reached an average lethality of 19% so far. However, unlike what happened with influenza A (H5N1) virus is considered a low pathogenic bird (LPAI: Low Pathogenicity Avian Influenza), hindering the detection of infected birds. For this reason, we must be prepared for immediate urgent diagnosis so they can take appropriate preventive measures.

The first case of HIV infection was detected in mainland China in March 2013, related to two deaths (one male of 87 years who developed symptoms on 19/02/13, 13/03/04 and died, and a man of 27 who fell ill and died on 13/2/27 3/13/10, both in Shanghai). From then until early May 2013, 132 have been detected casios, and the death toll was 29 (19% lethality). Cases detected so far, there have been only in China, most unrelated them, most with severe symptoms, and some have died .. Only two family clusters have occurred, no other cases of human transmission have been demonstrated, or in health personnel.

The source of infection is unknown, and does not appear to be related to animal outbreaks or clear exposure to them, although in some cases had epidemiological history of contact with animals, mostly chickens, have been detected infection in animal markets alive, and even a decrease in cases at the close of markets where live animals have been cases. It is currently investigating the possible transmission between animals and people, and person to person.

Clinically, the most important is that those affected have severe pneumonia with fever, cough, difficulty breathing , which required intensive care and mechanical ventilation.

Currently it is not known with certainty:

  • The source of human infection.
  • Seroprevalence Influenza A (H7N9) in humans and animals.
  • The possibility of human transmission, but found two family groupings.
  • The range of signs and symptoms of presentation.
  • The existence of asymptomatic infection.

How is this new subtype of influenza virus A (H7N9)?

The most characteristic and distinctive, this new subtype of Influenza A (H7N9) virus, which has been shown corresponding to a genetic recombination of several viruses Influenza A H7.

As is known, all Influenza viruses have eight genes which can recombine between two viruses, when these coincide infecting the same cell. These genes are PB2, PB1, PA, HA, NP, NA, M and NS.

Of these genes, the H7 gene is similar to a virus Influenza A (H7N3), wild ducks circulating in migratory routes of East Asia (type strain A / duck / Zhejiang / 12/2011).

The N9 gene is similar to an Influenza A (H7N9) virus, found in wild bird migratory routes in East Asia and Mediterranean (type strain: A / wild bird / Korea / A14 / 2011).

The PB2 gene, PB1, NA, NP and M, come from an Influenza A (H9N2) virus found in finches ( "brambling") (Type strain: A / brambling / Beijing / 16/2012).

The virus found in humans, recombinant genes contain an unknown host, and would have led to the human strain A / Anhui / 1/2013.

Precautionary measures

The same preventive measures that have been recommended for other severe respiratory infections caused by viruses (bird flu H5N1, pandemic influenza H1pdm09 virus, SARS, or new coronavirus EMC / 2012, avoiding contact with live animals, and perform washing recommended frequent hand, and intake of meat and poultry products cooked. So far, no government, no ña WHO has recommended restricting travel to China. No vaccines are available, although WHO has recommended investigating the selection of a suitable strain for the preparation of a vaccine if necessary. As treatment the use of neuraminidase inhibitors (oseltamivir or zanamivir) is recommended.


OM .S. He recommended to have the capacity and necessary preparations to detect infections by influenza A virus by a molecular process RT-PCR using primers ( "primers") to amplify a conserved gene (p. eg. Matrix), and other molecular tests to identify H1, H1pdm09, H3 and H5 subtypes. Currently it is incorporated subtyping of H7.

Likewise, the WHO recommends that full diagnosis on the same day can be done through a system of detection and confirmation.

Preservation and shipment of sample:

  • Refrigerated (preferred) for less than 2 days.
  • Frozen more than 48 hours.

Shipment to the laboratory:

  • Refrigerated.


Delivery term:


  • RT-PCR: 24 hours.
  • Molecular identification: 72 to 96 hours.


Cost of testing: