The lowdown on diphtheria and its resurgence

Updated - December 24, 2017 11:15 am IST

Published - December 23, 2017 08:27 pm IST

Health hazard: Patients suffering from symptoms of diphtheria undergoing treatment at Fever Hospital in Hyderabad. (File Photo)

Health hazard: Patients suffering from symptoms of diphtheria undergoing treatment at Fever Hospital in Hyderabad. (File Photo)

What is it?

Diphtheria is a highly infectious disease, which usually shows up as a sore throat and difficulty in breathing. It spreads through contact or cough and sneeze droplets, and is caused by the bacterium Corynebacterium diphtheriae. In severe cases, the toxin secreted by this bacterium kills cells in the throat, and the debris forms a wing-shaped grey membrane, disrupting breathing and earning diphtheria the name “The Strangling Angel.” If the patient isn’t treated quickly with anti-diphtheria serum, the toxin can spread through the bloodstream hurting the heart and kidneys.

Before the 1940s, when diphtheria vaccination grew widespread, millions of children died of the disease across the world. But as vaccination rates and sanitation improved, incidence dropped everywhere, including in India. Yet, India continues to be a world leader in diphtheria today, with 3,380 cases and 177 deaths reported in 2016. This year has seen worrying outbreaks in Karnataka, Kerala and Telangana, among other States.

How did it come about?

India has had a diphtheria vaccination programme since the 1980s. Despite this, we continue to do poorly in controlling the disease because the vaccination does not reach everyone. Under the Universal Immunization Programme (UIP), all children below one year of age are supposed to get three doses of the Diphtheria-Tetanus-Pertussis (DTP) vaccine, followed by two booster doses between 1-2 years and 5-6 years. But coverage of the three primary doses is inadequate at 80% across the country. Data on coverage with the two booster doses is patchy, with one Hyderabad-based study showing poor rates of around 60% and 36% for each dose, respectively, in 2006. This data explain why diphtheria is increasingly infecting adolescents and adults in India, though it was historically an illness of children under five. As primary vaccination coverage is improving steadily, booster coverage remains poor and there is no vaccination for grown-ups. Some countries like the U.S. recommend booster doses every 10 years to tackle waning immunity among adults. The link between low vaccination rates and disease is clear in all recent epidemics. For example, Bihar, which has a poor record of primary immunisation, saw 41% of its cases in the under-five age group, while Kerala, which has high rates of immunisation, saw 74% of cases in the above-10 age group, according to a WHO report. A review from Chennai’s National Institute of Epidemiology also found low rates of vaccination among Muslim communities, one of the reasons driving outbreaks in States like Andhra Pradesh. Kerala, despite its high vaccination rates, has susceptible pockets for the same reason. An outbreak in Malappuram this year seems to have been driven by anti-vaccination sentiments seeded by Islamic clerics in the district. These outbreaks have been worsened by stock-outs of the anti-diphtheria serum in these regions.

Why does it matter?

Any disruption of vaccination programmes can trigger a deadly resurgence of diphtheria, as historical precedents show. During the 1990s, an epidemic swept across the former Soviet Union, making 1,57,000 people ill and killing 5,000 in eight years. It was triggered by an ill-advised change in vaccination schedules and socio-economic instability after the dissolution of the Soviet Union. This year, the Rohingya refugee camps in Bangladesh saw large outbreaks owing to low rates of vaccination and overcrowded and unclean camp conditions.

What next?

The only answer is better vaccination. The director of the National Institute of Epidemiology, Manoj Murhekar, recommends in his 2017 epidemiological review that a dose of tetanus-diphtheria vaccine be given to children at school entry, because over 80% of all Indian children attend primary schools. Also, vulnerable communities like Muslims in Andhra Pradesh must be targeted with awareness campaigns.

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