[Influenza in Poland in 2004]. / Grypa w 2004 roku.

A total number of 336,919 cases of influenza and influenza-like illness registered in Poland in 2004 (incidence 882.4 per 100 000 population). Regionally the incidence ranged from 226.2 per 100 000 population in Podlaskie to 2,122.3 in Mazowieckie. Children and adolescents under 15 years of age accounted for 30.5% of all cases (age specific incidence 1,588.2 per 100,000). In this age group the incidence varied regionally from 388,7 in Slaskie to 3,718.2 in Mazowieckie. 1,038 patients (0.31% of all cases) required hospital admission. There were 27 deaths due to influenza, in 85.2% these were persons over 70 years of age. In the epidemic season 2003/2004 six strains of influenza A/H3N2 virus were isolated in Poland. Antigenic analysis performed by the National Influenza Center showed that they were similar to strains A/Panama/2007/99 and A/Korea/770/02. Besides, in other 8 cases influenza A infection was confirmed by direct immunofluorescence test.

[Various sides of influenza, part I--structure, replication, changeability of influenza viruses, clinical course of the disease, immunological response and laboratory diagnostics]. / Grypa w róznych aspektach. Czqsc I--Budowa, replikacja i zmiennosc wirusów grypy oraz przebieg kliniczny choroby, odpowiedz immunologiczna i diagnostyka laboratoryjna.

Influenza viruses represent Orthomyxoviridae family. Spherical virions are 80-120 nm in diameter and have two-layer lipid envelope. The following proteins are coded by 8 or 7 segments of the single-stranded RNA: nucleoprotein (NP), polymerase PB2, PB1 and PA, member protein--M1 and M2, glycoproteins--hemagglutinin (HA) and neuraminidase (NA). HA and NA form spikes on the virion surface. On the basis of antigenic differences there are distinguished three types of influenza virus-A, B and C. Besides, influenza A viruses occur in different subtypes, depending on the features of HA and NA. One of influenza characteristics is its antigenic changeability: antigenic drift and antigenic shift. Infection occurs by droplet route, sometimes through direct contact with infected person or surface. Influenza virus attacks epithelial cells of upper respiratory tract, where replication takes place resulting in the production of approximately 1000 of progeny virions during a single 6-12 h cycle in one cell. Necrosis of ciliary cells of mucosa facilitates invasion of bacterial pathogens. Incubation period lasts on average 1-2 days. Influenza illness without complications characterizes the sudden onset of respiratory symptoms and systemic symptoms. Regression of symptoms usually occurs after 3-5 days, but cough and malaise may be observed for over 2 weeks. Reasons for the severe course of the disease or even death are post-influenza complications, e.g. viral pneumonia and bronchitis, bronchiolitis in children, secondary bacterial pneumonia, otitis media, myocarditis and pericarditis, Reye's syndrome, myositis, myoglobinuria, neurological complications and exacerbation of existing chronic diseases. In the case of influenza there is no possible to make the unquestionable diagnosis only on the basis of clinical picture of the disease. Therefore in some circumstances there is important to make some diagnostic laboratory tests as RT-PCR, immunofluorescence assay or isolation of virus and detection of the specific antibodies. The main determinants of the immunity to influenza virus infection are antihemagglutinin (anti-HA) antibodies and antineuraminidase antibodies (anti-NA). The former play fundamental role for the protection against the infection, while anti-NA antibodies limit virus spreading and contribute to a milder course of the disease. In the response to influenza infection there are observed serum immunoglobulines IgG and IgM (after the first contact with the antigen), while immunoglobulines IgA are produced rarely. The latter are produced locally in the high concentrations on the mucus of respiratory tract. Cellular immunological response is important for recovery from influenza where a significant role of cytotoxic T lymphocytes should be emphasized. These lymphocytes are able to kill infected cells in the earliest phases of replication before the progeny virions are formed.

[Various sides of influenza. Part II--epidemiology, influenza surveillance and prophylaxis]. / Grypa w róznych aspektach. Czqsc II--Epidemiologia i nadzór nad grypq oraz profilaktyka.

Influenza viruses cause epidemics and pandemics. Animal reservoir for influenza viruses and repeatedly occurring human infections with avian influenza viruses since 1997 indicate that there is a real threat of pandemic, but it is no possible to predict when this outbreak begins. Every year 330-990 millions of people are ill due to influenza worldwide. In Poland there are registered from a few hundred to few millions of cases and suspected cases of influenza each epidemic season. WHO coordinates the international Global Influenza Surveillance Network consisting of international WHO reference centres for influenza in London, Atlanta, Tokyo, Melbourne and 115 national influenza centres in 86 countries all over the world. One of such National Influenza Centers is located in Poland at the National Institute of Hygiene in Warsaw Influenza surveillance provides information on the currently circulating strains of influenza viruses, including new variants and their spreading that allows to choose appropriate strains to include into the vaccine for the next epidemic season. Regional influenza surveillance networks also exist, as the European Influenza Surveillance Scheme (EISS). The epidemic season 2004/2005 was the first season when the integrated system of virological and epidemiological surveillance SENTINEL started to work in Poland, according to EISS indications. In this system there are included the selected family physicians representing the entire country, Voivodship Sanitary-Epidemiological Stations and the National Influenza Center. Data obtained by the SENTINEL system are then forwarded to EISS and WHO. Widely available way of prophylaxis against influenza is vaccination. Inactivated influenza vaccines prevent illness in 70%-90% healthy adults under 65 and in children. They also prevent post-influenza complications. Attenuated nasal influenza vaccines are registered to use in Russia and the United States. In Poland, vaccinations against influenza are considered in the Program of the Preventive Vaccinations as recommended since 1994. Vaccination against influenza is especially recommended for people who highly risk occurrence of post-influenza complications as well as for some groups of people due to epidemiological indications. Vaccine is administered before epidemic season, but it is also possible during the epidemic season when virus already circulates in the population. There are performed studies to improve currently vaccines, e.g. studies on the safe adjuvants (aluminium, MF59, virosoms), DNA vaccines, use of hemagglutinins and neuraminidase obtained by genetic recombination and expression in insect cells, studies on the production of influenza vaccines in the cell culture MDCK and Vero instead of currently used chicken embryos. There are available specific antiviral-antiinfluenza drugs of new generation: oseltamivir and zanamivir that are neuraminidase inhibitors and old generation drugs: amantadine and rimantadine that are inhibitors of M2 protein.