A computer program was written to analyse oligonucleotide patterns displayed by gel electrophoresis following restriction endonuclease digestion of human cytomegaloviral DNA, and was applied to an epidemiological study of the transmission of infection in a hospital special care baby unit, with regard to infant-to-infant and mother-to-infant transmission.

The program calculates the molecular weight of oligonucleotides from their mobilities, using a cubic spline curve based on the mobilities of oligonucleotides from the AD169 strain. A matching algorithm then calculates the number of unmatched fragments for each pair of viral isolates. This was used as a similarity measure which successfully distinguished mother and infant isolate pairs from epidemiologically unrelated pairs.

The program is not intended to provide fully automatic matching, but could be recommended as a screening device to pick out pairs of strains which are sufficiently similar to suggest a common source of infection, and which may warrant closer comparison. Other applications are discussed, and the possible use of densitometers to automate data entry is considered.

The nucleotide sequences of the haemagglutinin (HA) genes of influenza A (H3N2) isolates from the 1985–6 season in Japan along with those of several viruses isolated between 1982–5 from other countries were analyzed to determine the origin of the 1985–6 Japanese strains. The HA genes of these viruses consisted of 1762 nucleotides and had a three-nucleotide deletion downstream from the stop codon when compared to the sequences of earlier Hong Kong H3N2 viruses. An evolutionary tree of the HA genes of these viruses was drawn using the A/Bangkok/1/79 sequence as the starting point. Eight strains isolated from Asian and Pacific regions including Japan in the 1985–6 season (one in May) had the HA genes located closely on the evolutionary tree but away from those of the isolates in North America and Europe during the 1984–5 season, and a common ancestry for these viruses was suggested.

Rotavirus infection was demonstrated in 168 (29·3%) of 573 children hospitalized for acute diarrhoea in Rome between January 1982 and December 1984. Laboratory diagnosis of these infections was made by transmission electron microscopy and enzyme immunoassay techniques with an overall agreement of 91·3%. Astroviruses, adenoviruses and small round viruses were detected in the faeces of 36 patients (6·4%). Whereas in 1982 rotavirus positive patients were clustered in the winter and following spring, in the following years cases were recorded all year round. The median age of patients with rotavirus infections was 17, 10 and 11·5 months in 1982, 1983 and 1984, respectively. In addition, a smaller number of rotavirus positive cases were admitted in 1983 when compared to those admitted during the previous as well as the subsequent years. It is suggested that a herd immunity was induced in the population by epidemic spread of rotavirus in the first half of 1982.

Blood samples from 13 locations in the Pacific and South-East Asia were tested for evidence of infection with human T-cell lymphotropic virus type-1 (HTLV-1), human immunodeficiency virus (HIV-1), hepatitis B virus (HBV) and hepatitis delta virus (HDV). No samples were positive for antibody to HIV-1. Antibodies to HTLV-1 were found in samples from five locations, the maximum prevalence being 19%, in Vanuatu. Serological markers of HBV infection were found in all locations, the maximal prevalence being 88%, in Majuro, Micronesia. Antibodies to HDV in HBsAg positive sera were found in six locations with a maximum prevalence of 81% in Kiribati.

Avian rotaviruses were isolated from feral pigeon faeces treated with trypsin using roller tube cultures of mammalian cells. Two pigeon strains, designated as strains PO-8 and PO-13, produced a marked cytopathic effect (CPE), small intracytoplasmic inclusion bodies and high titres of infectious particles in infected MA-104 and MDBK cell lines without cell adaptation and roller drum apparatus. The pigeon rotaviruses shared a common group specific antigen with the Lincoln strain of bovine rotavirus by indirect immunofluorescence, but differed from both the Lincoln strain and the Wa strain of human rotavirus in neutralization tests.

The RNA segment profile of this virus on polyacrylamide gel electrophoresis differed from that of group A mammalian rotaviruses. The results of a serological survey suggested that antibody to pigeon rotaviruses was widespread in avian species in Japan.

In the UK surveillance of AIDS and HIV infection is based on routine reporting systems. Whilst attempts are made to ensure that AIDS data are as complete as possible, numbers of reports fluctuate from month to month for reasons which are described. In 1986 there was an increase in death certificates naming AIDS as a cause of death in patients who were not identifiable in the surveillance data. More active surveillance is now undertaken in order to minimize this and other possible discrepancies.

It is probable that most cases of AIDS are reported and therefore these data can be used to describe trends in the epidemic by ‘risk group’. Laboratory reports of HIV antibody-positive tests could give an earlier indication of trends because of the long incubation period of AIDS. But these laboratory data are difficult to interpret because they represent an incomplete and biased sample of all positive persons.

AIDS cases are still being reported at a rate which is increasing approximately exponentially. Short-term predictions are presented showing a growth in the epidemic which is consistent with previously published predictions. Most cases are in the homosexual risk group. New asymptomatic homosexual patients with HIV antibody are still being identified.

The epidemic of AIDS in haemophilia patients should be of finite size although new cases of AIDS are likely to continue to be diagnosed for several years. AIDS due to blood transfusion given in the UK before donor screening appears to be a much smaller epidemic. The epidemic in drug abusers is increasing. Heterosexually acquired AIDS and HIV infections are being reported in small but increasing numbers.

A 4 year survey was undertaken in 1982–6 to examine the seasonal nature of bluetongue virus activity in Malawi. Bluetongue infection at Bwemba in Lilongwe district and Likasi in Mchinji district, both in the Central Region of Malawi, was detected by examining sera taken from calves at each site, at monthly intervals. The proportion of seronegative calves undergoing serocon version each month was used as a measure of virus activity. At both sides bluetongue virus activity was found to be most marked during the rainy season, with no activity detected during the dry season from July to September. Thus the pattern of bluetongue infection in Malawi is highly seasonal. Examination of type-specific neutralizing antibody showed that the prevalent serotypes varied from year to year.

Thirty-one ponies immunized with inactivated virus vaccine containing A/equine/Miami/63 (H3N8) virus and six seronegative ponies were experimentally challenged with the homologous virus strain. All G unvaccinated ponies and 11 out of 31 vaccinated ponies became infected. A clear relationship between pre-challenge antibody, measured by single radial haemolysis (SRH), and protection was demonstrated as judged by virus excretion, febrile responses and antibody responses. Those ponies with SRH antibody levels > 74 mm2 were completely protected against challenge infection by the intranasal route.

Å. Örtqvist, Ulrika Ransjö and B. Wretlind

Plasmid analysis as an epidemiological tool in neiirosurgical infections with coagulase-negative staphylococci

Materials and Methods, subsection Reagents,

line 1: ‘25 M disodium EDTA’ should read ‘25 mM disodium EDTA’

line 1: ‘25 M Tris’ should read ‘25 mM Tris’

line 2: ‘lysostaphin 250 μm/ml’ should read ‘lysostaphin 250 μg/ml’

During the outbreak of influenza due to A (H3N3) viruses in Finland in 1985/6 virus pairs were isolated from the same clinical specimens in embryonated hens' eggs (CE) and in canine kidney cell cultures (MDCK). Some of these isolates, the E and M pairs, were distinguished by their reactions in haemagglutination inhibition (HI) tests carried out using polyclonal antisera, and by receptorbinding properties, as evidenced by differences in their elution activity from erythrocytes. Passage of the E- and M-virus isolates in the foreign host affected their serological characteristics, but the E virus did not convert to an M-like virus and the M virus did not convert to an E-like virus. Returning the viruses to grow in the host used for their isolation changed the serological reactions so that they were once more close to the reactions of the original isolates. This contrasts with the changes in receptor-binding properties. Rapid elution from hen erythrocytes, which has been described as a property of viruses binding to the SAα2,3Gal sequence in preference to SAα2,6Gal, characterized the virus passages grown solely in MDCK cell cultures. Cultivation of the M virus in CE, at any stage of its passage history, made the virus irreversibly incapable of elution. The M virus was more sensitive than the E virus to HI antibodies against heterologous viruses of the H3N2 subtype, and, when used as an antigen in HI serology, it more frequently (90% vs. 69%; P < 0·01) detected diagnostic antibody responses in patients infected with viruses of this subtype in 1985/6. Use of antigens with a different passage history in HI serology provided evidence that this superiority, which may be due to the ability of the virus to pick out anamnestic antibody responses, is unrelated to the receptor-binding peculiarity of the M virus under consideration. The results support the concept that the host cell can select a diversity of virus variant subpopulations from a single clinical specimen during isolation and subsequent cultivation procedures. Moreover, the MDCK-grown influenza viruses may correspond better than the egg-grown isolates to the natural epidemic viruses.

A total of 6346 swine sera collected at an abattoir in the city of Obihiro, Hokkaido during the years 1978–87 were tested for the presence of antibodies to swine and human influenza viruses. A high incidence of antibody to A/New Jersey/8/76 (swine type H1N1) virus was observed throughout the 10 years except for the occasional month and a single long period of 15 months. Antibodies to human H3N2 virus in swine appeared to be related to the epidemics of human influenza which occurred in the study area during the years 1980–3, but unrelated to the epidemics during the years 1984–7. A large number of swine were found to be antibody positive to a human H1N1 virus during the period April to June 1964, and a smaller number, during the period November 1986 to June 1987. Both were in relation to human influenza epidemics. However, there were long periods where human H1N1 antibodies in swine could not be found.

The first occurrence of swine influenza in Japan was recognized in 1977, when it was presumed that the disease was introduced via imported swine (Shibata elal. 1978). Further outbreaks of swine influenza and a high prevalence of antibody to the virus in Japanese swine populations have been reported by several workers (Yamane, Sukeno & Ishida, 1978; Sugimura elal. 1981; Ogawa elal. 1983). An outbreak of influenza virus infection due to an H3N2 strain was previously seen in a herd of swine in Osaka, Japan (Sugimura etal. 1975). Later the co-existence of swine (H1N1) and human (H3N2) influenza viruses was confirmed by serological and virological studies on Japanese swine populations (Onta et al. 1978; Sugimura et al. 1980; Arikawa et al. 1982). In a previous report (Miwa et al. 1986), we suggested that the swine became infected with a human H1N1 virus as piglets during an epidemic of influenza which occurred in the human population at the same time. The present study was undertaken to evaluate the changes in the prevalence of antibodies against swine and human influenza viruses in Japanese swine during the past 10 years.