We devised a quantitative assay for Epstein-Barr-virus-infected mononuclear leukocytes (virocytes) to determine their prevalence in the blood of patients with acute-phase and convalescent-phase infectious mononucleosis and in healthy Epstein-Barr-virus-seropositive controls. Mononuclear peripheral blood leukocyte suspensions were tested for virus-determined cytoproliferative activity by cocultivation with human cord-cell indicator cultures. The highest levels of virocytes among circulating mononuclear leukocytes were found in the early acute phase of infectious mononucleosis (up to 0.05 per cent). Virocytemia decreased to levels comparable with those of healthy controls (less than 0.00001 per cent) by the third month after onset of infectious mononucleosis. These findings provide a quantitative profile of the course of the infection at cellular level and support existing evidence of the efficiency of immune control mechanisms in limiting Epstein-Barr-virus infection during the course of infectious mononucleosis.

The antibody reactive in antibody-dependent, cell-mediated cytotoxicity (ADCC) to influenza virus-infected cells was measured in two groups of seven volunteers each, before and after immunization with inactivated or live attenuated A/Victoria/3/75 influenza virus vaccines. Age-matched controls were seven adult individuals who experienced natural influenza infection due to A/Victoria/3/75-like virus strain. After inactivated whole influenza virus immunization all the subjects showed a significant rise of the antibody reactive in ADCC (from a mean value of 4.7% to 17.1% cytotoxicity, before and 5 weeks after immunization, respectively) as well as of hemagglutination inhibition (HI) antibody (fourfold or greater increase). These immune responses were similar to those observed among naturally infected controls. After live attenuated virus vaccination, no significant increase in titer of antibody reactive in ADCC was detected, even though the vaccine induced significant increase of HI antibody titer. Little correlation was found between ADCC and HI antibody rises in sera of recipients of inactivated virus vaccine and of naturally infected individuals while, in live attenuated influenza virus vaccines, the rise of HI antibody titer did not correspond to a significant increase of ADCC antibody titer did not show subjects who developed a significant rise in ADCC antibody titer did not show significant variation in antibody to neuraminidase and/or to complement fixation influenza virus antigens.

Influenza activity was studied in the Rome population from 1956 to 1976 by analysis of mortality from respiratory causes and from all causes. During cold weather months, type A influenza virus was associated, as a rule, with epidemic excess deaths at two year intervals while type B virus was prevalent twice during isolation data were also compared with epidemic excess mortality during four consecutive years. The evidence obtained indicated that influenza virus isolation alone does not represent a reliable index of epidemic influenza activity in this population. The proportion of deaths attributed to respiratory causes consistently increased in every epidemic, the most pronounced increases occurring during large epidemics. The break-down by age of deaths from respiratory causes in the course of two epidemic periods showed that the percentage distribution of deaths was essentially the same as in non-epidemic periods. This evidence indicates that the same factors influencing the age-related distribution of mortality from respiratory causes during non-epidemic periods, probably affect the fatal outcome of influenza during epidemics.

The widespread use of any antimicrobial agent, including antiretroviral agents, has the potential to select drug-resistant populations of microorganisms. HIV drug-resistant strains have been recognized as a serious threat to the efficacy of current antiretroviral treatments and could jeopardize efforts to increase access to treatment in countries most affected by the HIV epidemic. The WHO Global HIV Drug Resistance Surveillance Programme aims at enhancing and enabling the response to the threat of antiretroviral drug resistance by assessing the geographical and temporal trends in HIV drug resistance, increasing our understanding of the determinants of HIV drug resistance, and identifying ways to minimize its appearance, evolution and spread. Based on a global network of experts and collaborating institutions, the programme is developing and field-testing tools and guidelines for the regular monitoring of the level and spread of HIV resistance, particularly in treatment-naive patients. Although relevant progress has been made, several important challenges still exist to the implementation of this essential and innovative programme.

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Immunization procedures with live attenuated and inactivated vaccines were carried out on a group of young recruits at the beginning of an outbreak of infection due to an A/Victoria/3/75-related virus strain, which occurred in February 1977 in a military camp. A retrospective investigation on protection from clinical influenza was then performed in order to investigate whether immunization with live virus vaccines, administered at the beginning of an epidemic, could provide early protection from the disease. In the course of the two weeks following vaccination, laboratory-confirmed clinical influenza cases occurred in 4 subjects among the 110 volunteers of the control group which received placebo, and in 8, 7 and 4 subjects respectively of the 3 groups of about 125 individuals, each of which received one of the following vaccine preparations: (a), live attenuated A/Victoria/3/75 influenza virus oral vaccine, grown on chick embryo kidney culture; (b), live attenuated nasal vaccine, a recombinant of A/Puerto Rico/8/34 with A/Victoria/3/75 virus; and (c), inactivated A/Victoria/3/75 virus intramuscular vaccine. These data do not support the hypothesis that, during an epidemic of infection, early protection from clinical influenza can be achieved through immunization with live attenuated or inactivated influenza virus vaccines, in spite of the high immunizing capability of the vaccine preparations.