Invasive Haemophilus influenzae disease in adults

Abstract

We reviewed retrospectively all invasive Haemophilus influenzae (Hi) infections in adults ascertained from reference laboratory records and notifications from five NHS regions over the 5 years from 1 October 1990, a period encompassing the introduction of routine Hib childhood immunization (October 1992). A total of 446 cases were identified, a rate of 0.73 infections per 10(5) adults per annum. Though numbers of Hib infections in adults fell after the introduction of Hib vaccines for children (P = 0.035), and there was no increase in infections caused by other capsulated Hi serotypes, total numbers of invasive Hi infections increased due to a large rise in infections caused by non-capsulated Hi (ncHi) strains (P = 0.0067). There was an unexpectedly low rate of infections in those aged 75 years or more (P < 0.0001). The commonest clinical presentations were pneumonia with bacteraemia (227/350, 65%) and bacteraemia alone (62/350, 18%) and the highest rates of disease were in the 65-74 years age group (P < 0.0001). Clinical presentation was not influenced by the capsulation status of the invading Hi strain. 103/350 cases (29%) died within 1 month, and 207/350 (59%) within 6 months of their Hi infection. Case fatality rates were high in all age groups. Pre-existing diseases were noted in 220/350 cases and were associated with a higher case fatality rate (82% vs. 21%, P < 0.0001). After the introduction of Hib immunization in children, invasive Hib infections in unimmunized adults also declined, but the overall rate of invasive Hi disease in adults increased, with most infections now caused by non-capsulated strains. Physicians and microbiologists should be aware of the changing epidemiology, the high associated mortality and high risk of underlying disease. Invasive haemophilus infections in adults should be investigated and treated aggressively.

An epidemiological study of Haemophilus influenzae at a Brazilian day care center

“…Surprisingly, we recovered only two Hi isolates from two different day care staff members (one in July, and one in December), even though we examined swabs from 23 adults each time. This was unexpected because high Hi carriage rates have been described in adults, especially NTHi strains [30]. Neither strain recovered was similar to those recovered from the children (data not shown).…”

Characterization of Encapsulated and Noncapsulated Haemophilus influenzae and Determination of Phylogenetic Relationships by Multilocus Sequence Typing

“…These isolates may also cause invasive disease, and serious non-Hib disease in children is more commonly due to noncapsulated isolates than to encapsulated isolates of the non-Hib serotypes (1,2,10,17). In some countries where the Hib conjugate vaccines are used (e.g., the United Kingdom) there has been an increase in adult invasive disease due to non-Hib isolates, most of which is due to noncapsulated isolates (34).…”

&lt;i&gt;Haemophilus influenzae&lt;/i&gt; type b vaccination: long-term protection

“…Além da grande diminuição de casos entre crianças imunizadas, já foi documentada redução da doença invasiva por Hib em indivíduos não imunizados com idade igual ou superior a 15 anos 56 . A proteção indireta estabelecida nessa faixa etária pode ser atribuída à chamada imunidade de rebanho, em que o efeito é estendido a grupos de uma comunidade, além dos grupos em que a ação preventiva foi implementada.…”