E-Paper
Understanding coronavirus and learning to live through the pandemic
It has now been six months since Sars-CoV-2, which causes the coronavirus disease (Covid-19), first emerged.
It has now been six months since Sars-CoV-2, which causes the coronavirus disease (Covid-19), first emerged. Within this short span of time, our knowledge about the virus, how it infects people, and what we must do to prevent it, has evolved dramatically. Here’s a ready reckoner on the disease.
SOURCES AND PROTECTION
Does it transmit over surfaces?
Contaminated surfaces such as doorknobs, grab rails, table tops or cash were once considered as potential sites of contamination. It now appears that fomite transmission – as this is called – is actually rare and not the primary mode of transmission, as per the United States’ Centres for Disease Control and Prevention.
This largely has to do with how the outer, spiked covering of the virus that it uses to infect human cells, which can easily get destroyed. But a large load of virus deposited on a surface, say after an infected person has sneezed, makes it risky to touch.
Do masks and face shields help?
Yes. The primary source of infection is through infected droplets when people speak, cough or sneeze. Wearing a mask – even a non-medical face covering -- reduces the possibility of inhaling the infected droplets quite significantly. Masks with an exhalation valve – something anti-pollution masks usually have – aren’t that effective.
The World Health Organisation (WHO) recommends that vulnerable people should wear a medical-grade mask and doctors should wear face shields since they are prone to being exposed to the virus, which can also be absorbed by the body through the membrane in the eyes.
How does washing hands help?
Hand-washing six to 10 times a day lowers the risk by 36% compared to those who wash them less than five times a day, a University College London study found. When water is not available, clean hands with alcohol-based hand rubs (with over 70% alcohol content).
However, even when properly done and combined with sanitising, this doesn’t offer complete protection, according to a review of 172 studies from 16 countries published in The Lancet on June 2.
Where should we be most careful?
Recently, the Lancet Infectious Diseases journal found that the virus spreads readily among household contacts even when someone is yet to develop symptoms.
Other risky settings include generally closed, indoor spaces – gyms, offices and restaurants, for instance – with hospitals and care homes being the most dangerous, since they are likely to be visited by infected people.
But some factors could help: being at distance in a large space that is well-ventilated cuts the risk.
Does this mean that it is less risky outdoors?
Possibly, but several ambient factors determine how far an infected droplet can go. Breeze, wind and air streams play a factor, and can theoretically transport them to longer distances. A good comparison is exhaled cigarette smoke, which a person is less likely to smell outdoors than in a closed room since diffusion happens more readily in the open.
The sun’s ultraviolet rays too can inactivate the virus.
But being close to an infected person in any setting – indoor or outdoor – is not ideal, thereby making social distancing crucial.
When does an infected person become infectious?
The incubation period, which is the time between exposure to Sars-CoV-2 and becoming infected with it, is on average five to six days, but has also been found to be as long as 14 days.
Infected people start becoming infectious before symptoms manifest. Studies show that they are most contagious one to two days before they begin to feel ill. There is no documented evidence on when asymptomatic people start infecting others.
Can those without symptoms infect you?
It appears to be so. A study of pairs of people in which one person definitely got infected from the other showed that about 44% of Covid-19 cases spread from person to person before symptoms appeared. This mirrors another study in which researchers isolated infectious virus from patients and found that it was produced before symptoms began to manifest.
This nature of this virus makes it particularly difficult to stop – asymptomatic and pre-symptomatic cases make the tracing and isolation of people even harder.
If there is a cluster near your house, are you more at risk?
If there are multiple cases in a neighbourhood, the odds of pre-symptomatic and asymptomatic people spreading infection when they meet others increases.
However, staying quarantined and using precautions like social distancing and wearing masks reduces risk.
DETECTING AN ILLNESS
When should you get tested?
Symptomatic people test positive more readily. Asymptomatic direct and high-risk contacts of a confirmed case should be tested between day 5 and day 10 of coming into contact with an infected person. Tests have to be done during a specific period to ensure there are no false negative results.
But no specific timeline has been identified since many can still throw up false negatives while having symptoms.
What are the tests used for diagnosis?
Indian Council for Medical Research (ICMR) has approved what is known as the reverse transcription polymerase chain reaction or RT-PCR test to detect genetic material (nucleic acid) of Sars-CoV-2 using swabs from the nose and throat of a person. It diagnoses an existing infection, so a negative result does not indicate you won’t get infected later. This is the gold standard test.
However, false negative results may occur, as was the case with Delhi health minister Satyendar Jain, if the sample is collected very early in the infection.
Last week, ICMR approved rapid antigen tests to detect current infection. Antigen tests, which take less than 30 minutes for results, check for protein signatures related to a Sars-Cov-2 infection.
A third type of test, antibody tests, see if someone has virus-fighting antibodies, the ones used so far have not been reliable.
How long after an infection do you test negative?
Most people with mild disease are no longer contagious 10 days after symptoms, and three additional days without symptoms, according to the WHO criteria for all Covid-19 cases, regardless of isolation location or disease severity.
Patients who are asymptomatic can end isolation 10 days after testing positive for Sars-CoV-2.
But there are outliers, such as a patient with mild Covid-19 in China who remained PCR-positive for 63 days after symptoms. It is unclear whether this posed a transmission risk.
NATURE OF ILLNESS
Who is most at risk?
Data from across the world shows severe disease and death rates are higher in people over the age of 65, living in nursing homes or long-term care facilities and with underlying medical conditions, such as chronic lung disease, asthma, heart conditions, obesity, diabetes, kidney disease, and liver disease. Risk is also high for people with compromised immunity because of cancer treatment, smoking, transplantation, immune deficiencies, prolonged use of corticosteroids and other immune weakening medications.
Fatality rates seen across the world show men are more vulnerable than women.
But infection can happen in anyone, including healthy people and children who can go on to develop fatal complications.
Are children and babies relatively safer?
Relatively few cases of babies with Covid-19 have been reported, and those who are infected have experienced mild illness, according to WHO. Children are 56% less likely than adults to get infected when in contact with an infected person, but how easily they pass on the infection to others is unclear.
In the US and China, children under 18 years account for around 2% of diagnosed cases.
But there have been widespread reports of children and adolescents developing a multisystem inflammatory condition similar to the Kawasaki disease and toxic shock syndrome. Such cases would need intensive care.
When are you likely to show symptoms?
Symptoms usually appear 2-14 days after exposure to the virus, and may range from mild to severe, depending on the extent of exposure and the health of the person. Most common symptoms are fever, cough, shortness of breath and difficulty in breathing, which may be accompanied by fatigue, muscle or body aches, headache, loss of taste or smell, nausea or diarrhoea.
What happens if you have mild or no symptoms?
Around four in five people have mild illness and can recover at home without medical care. They need to stay isolated at home for two weeks to prevent spreading the infection to others around them.
When should you seek medical attention?
Emergency warning signs for Covid-19: trouble breathing, persistent pain or pressure in the chest, confusion, inability to wake or stay awake, and bluish lips or face.
