PANDEMIC FLU A/H1N1V: VIROLOGICAL SURVEILLANCE IN SOUTH TUSCANY

On April 24, 2004, the World Health Organization confirmed a number of cases of con- tagion of the new Influenza virus A/HIN1 in Mexico and the United States. On June 11 2009, the rapid spread of infection compelled the WHO to raise the pandemic phase to 6, which corresponds to the highest state of alert. The virus probably originated from a recent reassortment between a swine virus previously reassorted with three different viral strains (swine, avian, human) and a new viral strain similar to the Eu- roasiatic avian virus[1]. This unprecedented circulation of the new influenza virus was facilitated by travel and international exchanges and has reached, in the period of little more than six weeks, the same extent that had been present in previous pandemics in a period of six months, therefore making necessary the implementation of various strategies of Epidemiological and Virological Surveillance. During the pandemic sea- son, 866 pharyngeal swab samples of persons who presented influenza symptoms were gathered. The patients were then divided into different age groups: 0-4, 5-24, 35-54, 55-64 and ≥65 years of age. The virus’ RNA was extracted from each swab by using a specific kit. Afterwards the RNA was reverse transcribed in cDNA and ampli- fied in a single reaction of real-time PCR using the one-step kit recommended by CDC protocol. The analysis of the 866 pharyngeal swabs has shown the presence of 262 positive sample results for the new variant of the A/H1N1virus. Several parameters of this study have been taken in consideration: age groups, geographical distribution of infection in the three cities studied, the weekly trend of positive results which had shown up after a trip abroad, the incidence in local cases and the measure of infection of the virus among patients who came in contact with infected persons. Among the examined age groups, those majorly affected are: ages 0-4, 5-14, 15-24, the least affected age group was ≥65. In conclusion, the data demonstrates that the age group mainly affected is that between ages 0-24. Presumably such data is justified by considering that the immune system of younger people has never come in contact previously with the variants similar to the A/H1N1, whereas older adults would seem to be less sus- ceptible, probably because they have already come in contact with similar viruses. The obtained data illustrates an elevated level of contagiousness among individuals, since the new influenza virus A/H1N1 of 2009, represents a variant of completely different from other H1N1 viruses that had previously circulated in the human species. It should be pointed out that the hemagglutinin differs by 27.2% and the neuraminidase by 18.2% compared to the amino acid sequence of the 2008 H1N1 influenza virus and by the variant of the viral strain used for the production of the vaccine, this lent to a sig- nificant pandemic potential. The trend of positivity in local cases from the 29th week was kept at medium-low levels until the 38th week with a great increase, probably due to the reopening of schools and offices after the summer break.