No information is available on influenza virus infections transmitted by blood or blood products. Due to the high antigenetic variability of influenza viruses, the continuously emerging drift variants can cause annual influenza epidemics.
For this reason, influenza vaccines must be adapted to the current drift variants each year and used in vaccinations to provide highest possible protection. The WHO provides recommendations on the antigen composition of the vaccine before each influenza season.
People are protected by the vaccine after 2 weeks. No reports are available on influenza virus infections by blood products. Three antiviral products for the treatment of influenza virus infections are authorised in Germany. Due to adverse reactions, the M2 ion channel blocker amantadine is hardly used. Rimantadine, another member of this class of active ingredients, has fewer side-effects, but is not authorised in Germany. These adamantanes are only effective against influenza A viruses and very rapidly contribute to the development of resistant virus variants [ 43 ].
The markedly more effective neuraminidase inhibitors oseltamivir and zanamivir can help shorten the phase of the disease and reduce the symptoms if administered in time within 24 h after the occurrence of the symptoms if possible [ 44 ]. Nearly all H5N1 isolates from Vietnam and Thailand were adamantine-resistant, whereas most of the H5N1 isolates from Indonesia and China were adamantine-sensitive [ 45 ].
The majority of H5N1 viruses from South-East Asia from were sensitive to the neuraminidase inhibitors oseltamivir and zanamivir. A number of H5N1 isolates were also sensitive to both classes of antiviral substances [ 19 ]. Both human and H5N1 viruses may show resistance to oseltamivir, but may be sensitive to zanamivir [ 46 , 47 ]. Therefore, continued resistance testing should be carried out both for human and for H5N1 strains.
Influenza is typically transmitted by air or direct contact. Transmissions of human influenza viruses by blood and blood products have so far not been reported, not even during pronounced influenza epidemics. No reports are available so far which show any evidence for a transmission of human influenza viruses by blood products or plasma components. The symptoms of an infection with human influenza virus give rise to the assumption that extrapulmonary tissue is infected, which is caused by viraemia.
Such a viraemia could be identified several times by isolation of the viruses from the blood. Virus isolation could not only be performed during the symptomatic phase of serious courses of infection [ 49 ], but also as early as before the onset of the clinical symptoms during a normal course of the disease [ 50 , 51 ].
These detections of virus, however, remain limited to isolated cases. So far, only few data is available on the occurrence of viraemia during an H5N1 infection. However, since severe diarrhoea could be observed in which virus detection was positive, it must be assumed that viraemia can occur with this virus type as well. Such a viraemia is observed in connection with high viral load and fatal outcome [ 52 ]. Whether the cases available are isolated cases or whether a general statement can be made remains to be clarified.
In conclusion, it can be stated that viraemia is possible in case of an influenza virus infection, even though the probability is low for the human virus type in case of a normal course of the disease. For H5N1 infections, the situation is judged differently: Based on the prolonged incubation period of up to 7 days and the apparently more frequent dissemination of the viruses in the blood, the risk potential is rated higher.
What remains unclear, however, both for human and for avian influenza viruses, is whether the introduction of virus into the blood circulation will lead to an infection of the blood recipient. In case of a natural infection, the influenza viruses enter the body via the respiratory epithelium where they replicate. So far, available data on the effectiveness of transmission via the blood are not sufficient. This question should be taken into account in future studies.
Influenza viruses belong to the group of enveloped viruses and are, therefore, inactivated by lipid solvents which are also used e. Transmission of influenza viruses by plasma derivatives can therefore be ruled out, above all thanks to the use of physical and chemical depletion and inactivation steps during manufacture [ 53 ].
In principle, human influenza isolates can be used for the validation of the manufacturing procedures for plasma components. According to the present state of knowledge, viraemia is observed only in serious courses of infection with human influenza viruses. This viraemia can usually be detected only as late as the first occurrence of symptoms of the disease such as fever. It can be assumed that H5N1 infections in humans involve viraemia.
Nothing is known about the onset of this viraemic phase following infection. Since the incubation period is 1—7 days for previously observed cases of disease, and is, as a rule, 2—5 days, it can be assumed that the viraemic phase is 7—10 days. In principle, it can be assumed that plasma components are safe both with regard to human influenza viruses and with regard to avian influenza virus.
Special steps during the annual influenza epidemics with human influenza viruses with regard to safety of cellular, non-inactivated blood components are not indicated. For the pandemic case, a framework should also be created enabling the blood donor services to co-ordinate their work as fast as possible.
Plans have been made to establish an agreement pursuant to section 3 subsection 2 of the Transfusionsgesetz German Transfusion Act laying down the details of mutual support in the event of disasters and other emergencies.
Such an agreement is currently being compiled by the organisations that run the blood donor services. Brunhilde Schweiger Robert KochInstitut. National Center for Biotechnology Information , U. Journal List Transfus Med Hemother v. Transfus Med Hemother. Copyright and License information Disclaimer. Karger GmbH, Freiburg. This article has been cited by other articles in PMC. Table 1 Pandemic phases according to the WHO pandemic preparedness plan [ 39 ]. Inter-pandemic period Phase 1 No new influenza virus subtypes have been detected in humans.
An influenza virus subtype that has caused human infection may be present in animals. If present in animals, the risk of human infection or disease is considered to be low. Phase 2 No new influenza virus subtypes have been detected in humans. However, a circulating animal influenza virus subtype poses a substantial risk of human disease.
Pandemic alert period Phase 3 Human infection s with a new subtype, but no human-to-human spread, or at most rare instances of spread to a close contact.
Phase 4 Small cluster s with limited human-to-human transmission, but spread is highly localised, suggesting that the virus is not well adapted to humans.
Phase 5 Larger cluster s but human-to-human spread still localised, suggesting that the virus is becoming increasingly better adapted to humans, but may not yet be fully transmissible substantial pandemic risk. Pandemic period Phase 6 Pandemic: increased and sustained transmission in general population.
Decisions to be made in Phase 6 whether a country is not yet affected, a country is affected or has close trade relations or travel between an affected country, activity has decreased, or a second pandemic wave has occurred Post-pandemic phase Return to inter-pandemic period.
Open in a separate window. Special Situation during the Pandemic Period Donor screening with nucleic acid amplification techniques for the detection of viraemia cannot be introduced immediately from a technical point of view.
Special Situation during the Pandemic Period To prevent masses of people from meeting in one site, special appointments should be made for blood collection activities. Reinhard Burger Dr. Christian Drosten Dr. Margarethe Heiden PD Dr. Martin Hildebrandt Prof. Bernd Jansen Dr. Horst Klamm Dr.
Thomas Montag-Lessing Dr. Ruth Offergeld Prof. Georg Pauli Prof. Rainer Seitz Dr. Uwe Schlenkrich Dr. Volkmar Schottstedt Dr. Hannelore Willkommen Prof. References 1. Fields Virology. Philadelphia: Lippincott Williams and Wilkins; Scholtissek C. Stability of infectious influenza A viruses at low pH and at elevated temperature. Characterization of a novel influenza A virus hemagglutinin subtype H16 obtained from black-headed gulls. J Virol. Cocirculation of two distinct evolutionary lineages of influenza type B virus since Evolutionary characteristics of influenza B virus since its first isolation in dynamic circulation of deletion and insertion mechanism.
Arch Virol. On the origin of the human influenza virus subtypes H2N2 and H3N2. Avian-to-human transmission of the PB1 gene of influenza A viruses in the and pandemics. World Health Organization: Avian Influenza. Influenza A outbreak among adolescents in a ski hostel.
Fatal influenza A virus infection in a child vaccinated against influenza. Pediatr Infect Dis J. Community-acquired pneumonia in Christchurch and Waikato — microbiology and epidemiology. Influenza pneumonia: a descriptive study. Fatal avian influenza A H5N1 in a child presenting with diarrhea followed by coma.
N Engl J Med. Webster RG. However, variant influenza virus infections also can cause serious illness, resulting in hospitalization and death.
Seasonal flu vaccines are not formulated to protect against variant influenza viruses, but the same flu antiviral drugs used to treat seasonal flu can be used to treat variant influenza virus infection in children and adults. In , these infections became nationally notifiable. Since that time, a total of variant influenza virus infections of different influenza A virus subtypes have been identified in the United States and reported to CDC ranging from a high of variant influenza virus infections during the flu season to a low of one during the and seasons The infections reported during the seasons included H3N2v, four H1N2v, and two H1N1v viruses detected during the influenza season.
Following that season, CDC implemented significant education and outreach efforts to raise awareness about the public health concerns related to exposure to pigs. Since then, identification of variant influenza virus infections has been less common, particularly for those associated with agricultural events. Influenza viruses can spread from pigs to people and from people to pigs.
Infected pigs can cough or sneeze and droplets with influenza virus in them can spread through the air. If these droplets land in your nose or mouth, or are inhaled, you can be infected.
Pigs can be infected by avian influenza and human influenza viruses as well as swine influenza viruses. When influenza viruses from different species infect pigs, the viruses can reassort i. This is thought to have happened in when a new H1N1 virus with genes of avian, swine and human origin emerged to cause a flu pandemic. CDC has guidance for people who work or interact with pigs and for people attending fairs where pigs might be present, including additional precautions for people who are at increased risk of serious flu complications.
In general, the risk to the public from these infections is considered low, but each case of human infection with a variant influenza virus should be fully investigated to be sure that such viruses are not spreading in an efficient and ongoing way in humans, and limit further exposure of humans to infected animals if infected animals are identified.
There are 18 different HA subtypes and 11 different NA subtypes. Subtypes are named by combining the H and N numbers — e. Click on the image to enlarge the picture. There are four types of influenza viruses: A, B, C and D. Human influenza A and B viruses cause seasonal epidemics of disease known as flu season almost every winter in the United States. Influenza A viruses are the only influenza viruses known to cause flu pandemics, i. A pandemic can occur when a new and different influenza A virus emerges that both infects people and has the ability to spread efficiently among people.
Influenza C virus infections generally cause mild illness and are not thought to cause human epidemics. Influenza D viruses primarily affect cattle and are not known to infect or cause illness in people. Influenza A viruses are divided into subtypes based on two proteins on the surface of the virus: hemagglutinin H and neuraminidase N. There are 18 different hemagglutinin subtypes and 11 different neuraminidase subtypes H1 through H18 and N1 through N11, respectively.
Reassortment can occur when two influenza viruses infect a host at the same time and swap genetic information. This graphic shows the two types of influenza viruses A and B that cause most human illness and that are responsible for flu seasons each year.
Both influenza A and B viruses can be further classified into clades and sub-clades which are sometimes called groups and sub-groups. Note that this graphic is an example, and currently circulating influenza clades and subclades may differ from those presented here. Figure 1 — This is a picture of a phylogenetic tree. Each sequence from a specific influenza virus has its own branch on the tree. The degree of genetic difference between viruses is represented by the length of the horizontal lines branches in the phylogenetic tree.
The further apart viruses are on the horizontal axis of a phylogenetic tree, the more genetically different the viruses are to one another. An influenza clade or group is a further subdivision of influenza viruses beyond subtypes or lineages based on the similarity of their HA gene sequences.
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