Mankind’s battle against germs has a long and triumphant history. In 1967, WHO’s Donald Henderson devised a strategy to identify smallpox contacts and vaccinate these contacts—what is famously called the ‘ring vaccination strategy’. It was this strategy that wiped out smallpox from our planet. In fact, the history of smallpox eradication is a telltale example of targeted surveillance and containment that yielded rich dividends. John Snow’s ingenious approach in 1854 when he mapped the source of the cholera epidemic to a water pump in Broad Street, London, is another epidemiological breakthrough that focused on source identification and disease containment.
Henderson and Snow’s battles against germs were won through targeted public health measures. Targeted public health measures are those that are deployed on segments of population carrying the infection and acting as reservoirs of disease. In the case of COVID-19 in India, this segment of the population is people with a history of foreign travel and their close contacts. Segregating, isolating, testing and treating this segment of the population is what is required for disease containment. Lockdowns alone may not be the perfect answer to the problems created by germs. There are other tactical weapons that need to be deployed in the battle.
Tedros Adhanom Ghebreyesus, Director-General of WHO, has said: “To slow the spread of COVID-19, many countries introduced ‘lockdown’ measures. But on their own, these measures will not extinguish epidemics.” To devise effective public health measures, one needs to have a proper understanding of virulence, pathogenicity and infectivity of a microbial organism. Infectivity is the rate at which a microbial organism spreads from one host to another. Pathogenicity refers to the ability of an organism to cause disease in the host. Virulence refers to the severity of disease caused in the host. Infectivity is denoted by a measure called “R0”. Latest data from the WHO estimated the “R0” for COVID-19 as 2.0 to 2.5, meaning infected individuals transmit it to 2-2.5 others on average.
By contrast, the “R0” for measles is 12-18, while for seasonal influenza it’s a little over 1. Also, COVID-19 may not have high pathogenicity as evidenced by the sizable number of asymptomatic or mildly symptomatic cases, especially in the younger and paediatric age-group. COVID-19 also has a relatively low virulence as evidenced by its low case fatality rate (CFR). In fact, the average CFR globally for COVID-19 is around 2.3 %. Comparatively, the CFR for Ebola was 50%, that for smallpox was 30%, and that for SARS was 9.4%. In essence, COVID-19 has moderate infectivity and pathogenicity, but low virulence. While fighting in a war, one needs to know the nature of the enemy. To succeed in this battle, we must have a keen insight into the germ’s biology and behaviour.
The bottom line is that we are dealing with a disease where 80% of those infected hardly need any medical care, 20% need just medical advice and about 5% need hospitalisation. The panic-stricken must understand that COVID-19 is a ‘self-limiting’ viral illness in the vast majority. Respiratory viruses don’t thrive and spread at the same rate all through the year. If they did, humanity would have been wiped out a long time ago! It is common knowledge that respiratory viruses have higher rates of infectivity during the winter months. Seasonal variations, temperature and climatic conditions do have an impact on the infectivity of respiratory viruses. Emerging reports that COVID-19 does not thrive well in hot, humid climates should give some comfort to people living in tropical regions of the world, especially with the summer fast approaching.
Therefore, mathematical modelling that forecasts millions of cases based on the initial rate at which COVID-19 spread during the winter months and in cold climates can blow the reality out of proportion. Clinicians on the ground can understand these realities better than statisticians, mathematical modellers and bench-side researchers. Also, India has one of the youngest populations in an aging world. The median age in India is just 28, compared to 37 in China and the US, 45 in Western Europe and 49 in Japan. This is India’s demographic dividend. This is also India’s demographic protection against COVID-19, which has selective virulence in the elderly. Notwithstanding these facts, we must use this opportunity to build a long-term arsenal in the fight against germs.
Hand hygiene and cough etiquette are universal precautions that must be followed at all times and not reserved only for an epidemic. The government must invest resources in long-term public health measures like enacting a legislation to ensure that all public restaurants, canteens and toilets have soap and tap water to facilitate hand washing. In fact, studies have shown that hand washing with soap and water at least three times a day (before meals) can reduce school absenteeism by as much as 50%. The government must also invest in public infrastructure that will decongest cities and prevent overcrowding in public places.
Mass congregations and political rallies where thousands of people gather must be disallowed. These are measures that will have a far-reaching impact on improving health and preventing disease. India must take a leaf from history and imbibe valuable lessons from public health battles fought and won by Donald Henderson and John Snow—both examples of targeted public health approaches. And then we can stop worrying and start living!
DR MADHU PURUSHOTHAMAN
Chairman, Glanis Institute of Medical Sciences, Madurai and attending physician, Memorial Hermann Hospital, Houston, US Email: madhu.purushothaman@gmail.com