HAEMOPHILUS INFLUENZAE B DISEASE
Last Updated : 8/6/2007
Nitin Shah
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Haemophilus influenzae type b infection

is one of the most common cause of invasive bacterial infection in < 5 yr old children. Mass vaccination against Hib led to virtual elimination of the disease from such countries like Finland, UK, USA etc (1,2). In developing countries like India, it is still a major cause of meningitis & pneumonitis as these countries can not afford mass vaccination programmes. There is an urgent need to establish the disease burden in such countries so that Govt. sponsored mass vaccination programmes can be started to decrease the disease burden due to Hib. This will help to eliminate or even eradicate Hib from world.

H. influenza organism
Haemophilus influenzae type b infection is one of the most common cause of invasive

bacterial infection

in < 5 yr old children. Mass vaccination against Hib led to virtual elimination of the disease from such countries like Finland, UK, USA etc (1,2). In developing countries like India, it is still a major cause of meningitis & pneumonitis as these countries can not afford mass vaccination programmes. There is an urgent need to establish the disease burden in such countries so that Govt. sponsored mass vaccination programmes can be started to decrease the disease burden due to Hib. This will help to eliminate or even eradicate Hib from world.

Epidemiology
95% of invasive disease due to H. influenza is caused by type b & 59% by type a or non-typable H. influenza. 95% of Hib occur in children < 5 yrs old. More is the % of population of children <5 yrs, more will be the number of cases of Hib per year in that country. Developing countries have both more incidence of Hib/100,000 in <5yr old children & more % of population <5 yr old. This leads to heavy disease burden on the otherwise fragile health care system. Male to female ratio in some studies is shown to be 2:1 in UK & 3:2 in India. (5)

It is estimated that 3 million cases of Hib infection occur every year world over and 0.375 million of them die due to Hib. Studies from west have indicated an annual incidence of 50-100/100000 in children <5 yrs of age as shown in Table 1 (2,6). 50-60% of total Hib presents as meningitis, 5-8% each as pneumonitis, epiglottitis, skin infections, bone infections, bacteremia & others. Whereas data from developing countries like India is meagre, the incidence varies from 100-250/100,000 in children < 5 yrs. Majority of them present as meningitis (70-90%) or pneumonitis (10-20%). Epiglottitis & skin infection of face virtually do not occur in developing countries. (2,6)

95% of invasive Hib disease occurs in <5 yrs old children. The peak occurs later in developed countries e.g. in Finland 28% of cases occur in <1 yr old & 40% in < 18 months old children. In UK, 44% occurs in <1 year old and 71% is <2 yr old children, in USA 38% occurs in < 1yr & 60% occur in <18 months old children, in Netherlands 37% occurs in <1 yr old (2,6). This means that the peak occurs at 9-18 months of age in such countries. This leads to less cases of meningitis (50-60%) & pneumonitis (<9% of total) whereas epiglottitis & facial skins infections occur in these countries. This is because older the child, more is the natural immunity & less is the severity of disease. Whereas in developing countries the peak occur early at 6-9 months e.g. in Gambia 84% of cases occur in < 1yr (49% < 6 months), in Senegal 69% occur < 1 yr (32% in < 6 months) & in Thailand 76% occur < 1 yr (50% in <6 months) (2,6). This leads to severe invasive disease as natural immunity is lacking in such young infants. This leads to more chances of meningitis (70-90%) & pneumonitis (10-20%) & virtual absence of epiglottitis & facial skin infections. It is interesting to note that epiglottitis & facial skin infections appear in such countries when the disease burden is reduced due to mass vaccination which leads to shift to older age for the peak. Even within countries there may be a difference in incidence depending upon the economical & socio cultural differences e.g. in Nerago USA, the annual incidence is upto <50/100,000 <5 yr with 81% of cases occurring in <1 yr old or Alaska where the incidence could be as high as <50/100000 <5 yr with 67% of cases occurring in <1 yr old children.(2,6)

Table I :

Incidence of Hib in various countries



Country Total Hib / 100,000<5yr  Hib  meningitis/ 100,000<5yr  Mass immunization Year  % drop / Year
 Finland 53 16-43 1988 - 89 100%/1991
 Netherlands >60 22 1993 85%/1994
 U. K. 60 - 120 25 1992 98%/1994
 U. S. A. 112 60 1989 - 93 99%/1995
 Iceland 63 43 1989 100%/1991
 Alaska 450 280-450 - -
 Gambia 60 - 270 60 - 70 - -
 Australia 59 25 1993 70%/1995
 Chile 50 - 70 25 - -
 Israel 35 18 - -
 India 80 - 100 50 - 60 - -


In India only hospital based data is available as shown in Table II. It shows that 30-45% of cases of meningitis & 8-12% of cases of pneumonitis are due to Hib (4,7). These values are similar to those seen in European countries before mass vaccination suggesting similar epidemiology. It is estimated that the annual incidence Hib in India is 50-60/100000<5yr (4). The IBIS study has shown that 76% occurs in <1 yr with peak at 6-9 months (range < 1 months to >9 yr old individual) (8).

Table II : Hospital based data on Hib meningitis in India

City / year Hib% Pneumococcus % Meningococcus  %
 Delhi (1981) 25 45 6
 Chennai(1994) 28 21 4
 Vellore (1985) 38 33 2
 Mean 31 29 4
 Of culture (%) (45) (43) (5)
 Pondicherry(1990) 8 30 ?


References

Contributor Information and Disclosures

Nitin Shah
Consultant Pediatrician and Pediatric Hemato-oncologist, B.J.Wadia Hospital for Children and Hinduja Hospital, Mumbai, India


First Created : 4/9/2001

References

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