244
Public Health SWINE INFLUENZA VIRUS AND THE RECYCLING OF INFLUENZA-A VIRUSES IN MAN N. MASUREL
Department of Virology and W.H.O. Influenza Centre, University Rotterdam, Rotterdam, The Netherlands
I have sought to establish the antibody pattern to swine influenza virus in various age-groups of the Dutch population. Furthermore, a vaccine study originally set up in 1973 to establish the efficacy of influenza vaccines in man9 provided an opportunity to assess the antibody response to swine influenza virus following immunisation with human H3N2 viruses. Finally, antibody responses to swine virus after infection with H3N2 viruses were studied in routine laboratory sera.
Erasmus
MATERIALS AND METHODS
Sera collected in 1967 and 1972 from Summary people in the 0-100 age-group showed hæmagglutination-inhibition (H.I.) antibody to swine virus A/Iowa/15/30 (Hsw1N1) in greatest number and with highest titre in people born before 1918. A slight decrease was observed from 1967 to 1972 in the number of sera with antibody to swine virus and in the height of the titres. The recently isolated A/New Jersey/10/76 (Hsw1N1) virus showed a result comparable to that of the Swine/1930 virus in sera of 1972. On the analogy of the findings in 1968, when the Hong Kong virus became epidemic in human populations and antibody to this virus was found in sera of people over 70 years, the suggestion is made that the recurrence of swine virus as an epidemic agent of human influenza may be expected around 1986. Fourfold or greater increase of antibody to Swine/1930 virus was observed in about 4—5% of people infected by or immunised with H3N2 viruses. This response occurred in people who had been in touch with the epidemic influenza-A viruses Hsw1N1, H0N1, and H1N1 during the swine era of 1918 to 1956. Following immunisation with H3N2 viruses of persons showing no response to H3N2 viruses in their serum 5% did show a fourfold or greater heterotypic H.I. antibody rise to swine virus. This finding is of consequence for the diagnostic serology of influenza.
Population In the
Sera
autumn
of 1967 and of 1972, 1497 and 2910 blood-
samples, respectively, collected from people aged 0-100 years, were provided by Dr J. H. Bekker and Dr J. Rechsteiner of the Public Health Laboratories stored at -20°C.
at
Bilthoven. The
sera were
Vaccination Sera In the autumn of 1973 a trial was initiated to inoculate 2000 volunteers with five different plain influenza vaccines, containing influenza A (H3N2) and B viruses. Sera collected on the day of inoculation and three weeks later were titrated in the haemagglutination-inhibition (H.I.) test against the A/England/42/72 (H3N2) virus and the A/Port Chalmers/l/73/ (H3N2) virus.9 For this study the sera were tested for antibodies to the swine virus A/Iowa/15/30 (Hsw1N1).
Routine Sera 67 paired sera of people with an influenza infection, demonstrated during the winter epidemics of 1973, 1974, and 1975 by isolation of H3N2 virus and a fourfold antibody rise in complement-fixation (c.F.) and/or H.I. test, were titrated against A/Iowa/15/3fl (HswlNl) virus.
INTRODUCTION
SINCE the first isolation of influenza-A virus in man1 an antigenic relationship has been established between influenza viruses of human and of aniIIJ mal populations. Distinct examples are the relationship between the Kong/1968 (H3N2) virus and the equine virus of 1963 (Heq2Neq2), and the serologically established relationCl. ship between the swine virus of 19302 and the virus causing the pandemic of 1918-19. The swine virus has been related to the 1918 pandemic in
Hong
numerous
studies.3-6
The first
indication, based on serological studies, that swine virus would recur in later years was given by Hena1.4 Masurel and Marine’ sugthat the swine influenza virus gested would recycle over a period of 70 years, thus probably reappearing by 1985-90. The ability of swine influenza virus to infect humans and on a small scale to spread from man to man has most recently been observed in the U.S.A.8 nessy
et
AGE-GROUP(y) OOOM
CCQt
Public Health SWINE INFLUENZA VIRUS AND THE RECYCLING OF INFLUENZA-A VIRUSES IN MAN N. MASUREL
Department of Virology and W.H.O. Influenza Centre, University Rotterdam, Rotterdam, The Netherlands
I have sought to establish the antibody pattern to swine influenza virus in various age-groups of the Dutch population. Furthermore, a vaccine study originally set up in 1973 to establish the efficacy of influenza vaccines in man9 provided an opportunity to assess the antibody response to swine influenza virus following immunisation with human H3N2 viruses. Finally, antibody responses to swine virus after infection with H3N2 viruses were studied in routine laboratory sera.
Erasmus
MATERIALS AND METHODS
Sera collected in 1967 and 1972 from Summary people in the 0-100 age-group showed hæmagglutination-inhibition (H.I.) antibody to swine virus A/Iowa/15/30 (Hsw1N1) in greatest number and with highest titre in people born before 1918. A slight decrease was observed from 1967 to 1972 in the number of sera with antibody to swine virus and in the height of the titres. The recently isolated A/New Jersey/10/76 (Hsw1N1) virus showed a result comparable to that of the Swine/1930 virus in sera of 1972. On the analogy of the findings in 1968, when the Hong Kong virus became epidemic in human populations and antibody to this virus was found in sera of people over 70 years, the suggestion is made that the recurrence of swine virus as an epidemic agent of human influenza may be expected around 1986. Fourfold or greater increase of antibody to Swine/1930 virus was observed in about 4—5% of people infected by or immunised with H3N2 viruses. This response occurred in people who had been in touch with the epidemic influenza-A viruses Hsw1N1, H0N1, and H1N1 during the swine era of 1918 to 1956. Following immunisation with H3N2 viruses of persons showing no response to H3N2 viruses in their serum 5% did show a fourfold or greater heterotypic H.I. antibody rise to swine virus. This finding is of consequence for the diagnostic serology of influenza.
Population In the
Sera
autumn
of 1967 and of 1972, 1497 and 2910 blood-
samples, respectively, collected from people aged 0-100 years, were provided by Dr J. H. Bekker and Dr J. Rechsteiner of the Public Health Laboratories stored at -20°C.
at
Bilthoven. The
sera were
Vaccination Sera In the autumn of 1973 a trial was initiated to inoculate 2000 volunteers with five different plain influenza vaccines, containing influenza A (H3N2) and B viruses. Sera collected on the day of inoculation and three weeks later were titrated in the haemagglutination-inhibition (H.I.) test against the A/England/42/72 (H3N2) virus and the A/Port Chalmers/l/73/ (H3N2) virus.9 For this study the sera were tested for antibodies to the swine virus A/Iowa/15/30 (Hsw1N1).
Routine Sera 67 paired sera of people with an influenza infection, demonstrated during the winter epidemics of 1973, 1974, and 1975 by isolation of H3N2 virus and a fourfold antibody rise in complement-fixation (c.F.) and/or H.I. test, were titrated against A/Iowa/15/3fl (HswlNl) virus.
INTRODUCTION
SINCE the first isolation of influenza-A virus in man1 an antigenic relationship has been established between influenza viruses of human and of aniIIJ mal populations. Distinct examples are the relationship between the Kong/1968 (H3N2) virus and the equine virus of 1963 (Heq2Neq2), and the serologically established relationCl. ship between the swine virus of 19302 and the virus causing the pandemic of 1918-19. The swine virus has been related to the 1918 pandemic in
Hong
numerous
studies.3-6
The first
indication, based on serological studies, that swine virus would recur in later years was given by Hena1.4 Masurel and Marine’ sugthat the swine influenza virus gested would recycle over a period of 70 years, thus probably reappearing by 1985-90. The ability of swine influenza virus to infect humans and on a small scale to spread from man to man has most recently been observed in the U.S.A.8 nessy
et
AGE-GROUP(y) OOOM
CCQt
