As states plan to exit the national lockdown and restricted travel resumes, social distancing, wearing masks and washing hands will be the only defence against the coronavirus disease (Covid-19). With infections likely to rise after restrictions are relaxed and the anticipated second wave hitting the world, some amount of social distancing will have to continue through 2022, said Harvard researchers in the journal, Science, on Wednesday.
In India, even with states planning to move towards a staggered lifting of the lockdown, the number of cases will continue to rise because the absolute number of cases is high. How the outbreak evolves over the next few weeks will depend on the lessons learned so far from infection trends, including clustering.
“You can’t police social distancing; people must learn to protect themselves. The acid test will be how we behave as we exit from the lockdown in the next few days,” said Dr Ambarish Dutta, associate professor of epidemiology and public health, Indian Institute of Public Health, Bhubaneswar.
“Studies show infected people take on average five to six days to develop symptoms, but are infective from day one. Some people have no symptoms and others have mild disease, but still infect others. Lockdowns prevent undiagnosed infected people from stepping out and infecting others, but with less restricted travel, chances of exposure increase, so we need to be extremely cautious,” said Dutta.
As India prepares to loosen lockdown measures, knowing who is most at risk of infection is critical. India has finally begun population-level surveillance of random samples, with pool testing for current infection and antibody testing for past infection, to help guide policy and help people protect themselves.
The world’s first study on who is at risk of both infection and severe disease shows that older people, men, obese people, the poor, those living in densely populated areas, and people with chronic kidney disease are more likely to test positive for Covid-19.
Unlike previous studies that have established trends from hospital data for the people with severe symptoms, the study, published in The Lancet Infectious Diseases journal, analyses electronic health records of 3,802 people who visited doctors’ clinics in England between January 28 and April 4.
“The risk of infection among the general population remains a grey area. It’s important to know which groups in the wider community are most at risk of infection so that we can better understand SARS-CoV-2 transmission and how to prevent new cases,” said study author professor Simon de Lusignan from the University of Oxford, and director of the Royal College of GPs Surveillance Centre, UK.
Hospital-based studies have found that being older, male, and having underlying diseases like hypertension and diabetes cause more severe disease and death. The Lancet study has found that most underlying diseases such as hypertension, diabetes and heart disease did not raise susceptibility to infection, as neither did household size.
The only clinical conditions associated with higher susceptibility to infection was chronic kidney disease and obesity. Of 207 people with chronic kidney disease, 32.9% tested positive, compared with 14.4% without kidney disease. Around 20.9% people who were obese tested positive, compared with 13.2% people with healthy weight.
The study also found smokers were less likely to test positive than non-smokers, which study authors said was due to confounding factors and because of a protective effect of smoking. “This result does not indicate that smoking protects against infection, and there are many potential alternative explanations – such as smoking hampering the sensitivity of the Sars-CoV-2 test, or smokers being more likely to have chronic cough so being more likely to be tested despite not having the virus. Apart from the well-documented health damage from smoking, smoking increases the severity of Covid-19, and so our findings should not be used to conclude that smoking prevents Sars-CoV-2 infection, or to encourage smoking,” said professor de Lusignan.
The study confirmed earlier findings of older people and men being at higher risk of disease. People between the ages of 40 and 64 years were at the greatest risk of testing positive (18.5%), compared with children younger than 17 (4.6%). Around 18.4% men tested positive, compared with 13.3% of women, which suggests that gender differences in poor outcomes are in part related to differential infection susceptibility.
Two preprint studies that examined population level risks showed increased risks of Covid-19 deaths in hospitals with older age, male sex, obesity, and poverty. Underlying diseases such as hypertension and diabetes and smoking play a more important role in disease progression and poor outcomes in hospital studies than in developing infection, The Lancet study suggests. The study did not measure socioeconomic factors that raise infection risk, including high-risk jobs such as health and municipal workers.
Going out with protection and social distancing is safer than being in a closed environment with infected people because the wind disperses the virus and the sun and humidity make it less transferable in sparsely populated areas.
The chances of getting infected from contaminated surfaces such as doors, railings, elevator buttons, table tops and shelves in shops and public places is high, as washing hands and avoiding touching your mouth, nose, eyes or the part of the mask that covers your face is crucial.
What works in India’s favour is its demography. “Most of India’s workforce, including the migrants going home, is predominantly young and are likely to recover and become non-infective very quickly. In countries like Italy and Spain, the deaths have been predominantly in older people in care homes,” said Dutta.
“The challenge for India will be preventing infection in public transport, retail markets and wholesale markets, which can seed large outbreaks, as evident from Chennai and Delhi wholesale mandis,” he said.