Clinical and epidemiological features of an outbreak of influenza in Ulan Bator in 1971.

In October and November 1971 an outbreak of influenza (type A virus) occurred in the town of Ulan Bator. A clinical and epidemiological investigation showed that some 30% of the population presented typical signs of influenza of medium severity. The etiology of the outbreak was confirmed by virological, serological, and fluorescent-antibody techniques.

Haemagglutination-inhibiting activity to type a influenza viruses in the sera of wild birds from the far east of the USSR.

The discovery in migrating birds of influenzaviruses and the demonstration of relationships between strains found in man and in birds show the importance of these investigations for influenzavirus ecology. Investigation of birds in the far-east regions of the USSR is particularly important as many of them migrate to South-East Asia and China, the regions from which human influenza pandemics seem to originate. A total of 262 bird sera from these regions were titrated by the HI method with 20 different influenzavirus antigens (5 human, 2 equine, 1 swine, and 12 avian influenzaviruses).

Some observations on the circulation of influenzaviruses in domestic and wild birds.

Four viruses isolated from poultry in the USSR and Poland were identified as influenza A strains. One strain was closely related to fowl plague virus, the second showed an antigenic relationship to A/chicken/Scotland/59 (Hav5N1), and two others were antigenically related to A/duck/Ukraine/1/63 (Hav7Neq2) and A/duck/England/56 (Hav3Nav1). Antibodies to different strains of influenzavirus were detected in sera collected from poultry and from wild birds in the northern area of the USSR.

Influenza A2 and B in the USSR in 1966-67, and some aspects of global epidemiology of influenza.

An epidemic wave of influenza caused by the A2 virus was recorded in the USSR in the winter of 1966-67; this was the fifth wave since this pandemic strain first appeared. In contrast to the last wave of 1965, it developed simultaneously with, or followed, an epidemic of influenza B. The epidemic spread of influenza was observed for a period of 2 years in the USSR; influenza B prevailed in 1966, influenza A2 in 1967, and the two viruses spread at different speeds.