Earlier in May, the Ministry of Home Affairs put a cap on guests attending a wedding ceremony to 50. Kumar's reception had over 300 guests, with numbers increasing as the procession moved from Paliganj to Piplawan under the Naubatpur block, where the bride hailed from. "After the tipoff, we swung into action and started contract tracing all the guests. Over 360 people were tested," says Pandey.

The incident reportedly set off one of the biggest Coronavirus infection chains in Bihar, with 113 people testing positive. It was the state's first reported brush with a super spreader event (SSE). "We set up isolation centres and containment zones to house the infected people. Even after they recovered, we conducted follow-ups. It was accompanied by an extensive awareness programme." Pandey says the results are finally showing. "We have managed to control the outbreak and if this continues, we will soon be able to declare Paliganj COVID 19-free."

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Paliganj Block Development Officer Chiranjeev Pandey during an inspection visit

Although not strictly defined by the World Health Organisation (WHO), a super-spreader refers to an individual who is highly contagious and capable of transmitting a communicable disease to an unusually large number of uninfected persons. Certain situations typically contribute to this, including mass gatherings, crowded transportation like trains and buses, refugee camps, or closed settings like gyms and nightclubs. There have also been some incidents at sporting events and conferences, where a large number of people have become infected. It's not clear how many infections someone needs to spur to qualify as a super spreader, but infectious disease experts believe more than eight or 10 secondary cases constitute a superspreading event. For MERS, superspreading events have reportedly involved up to 82 secondary cases.

A winding queue for BEST and ST buses at the CSMT junction bus stop. PIC/SURESH KARKERA

As Mumbai, one of the worst affected cities in India, enters the fifth phase of unlocking the economy, with restaurants, bars and eateries set to open this week, the possibility of SSEs looms large. Ward officers and city administrators are trusting people to exercise social distancing measures, wear masks and sanitise themselves and their surroundings. "With more curbs being lifted, the onus is shifting from the administration to the common man. The responsibility of wearing masks and practicing distancing is now up to them. While we are raising awareness through the My Family, My Responsibility campaign, the system has its limitations," says BMC assistant commissioner Kiran Dighavkar, who serves Mumbai's G-North ward (Dadar, Mahim and Dharavi). As part of the government's statewide outreach programme, Majhe Kutumb, Majhi Jajbabdari, the health department is undertaking a door-to-door survey and testing oxygen levels of people.

Dighavkar is one of the officials whose quick action led to controlling the virus spread in one of the city's most densely populated areas, Dharavi. They managed this with aggressive contact tracing, launching awareness campaigns and holding health camps. Success in Dharavi has inspired them to shift focus to other pockets. "Now that outdoor games are being allowed, we are keeping a close eye on Shivaji Park because a lot of football and cricket matches take place there," he says. His primary concern in the coming months will be handling the crowds expected ahead of Navratri and Diwali. "We saw a massive rise in cases after Ganeshotsav; we don't want another such spike. So, our thrust will be awareness and house-to-house surveys."

(Right) Kiran Dighavkar with BMC commissioner Iqbal Singh Chahal during a visit to Dharavi 

With less than 20 days left for the Navratri festivities to begin, the state government has issued a circular advising the cancellation of indoor and outdoor garba, dandiya and cultural programmes, usually a mainstay of the festival that celebrates Goddess Durga. In the 16-point document, the state home department said festivals need to be celebrated in a "simple manner". This year, Navratri starts on October 17, with Dusshera falling on October 25.

Despite the continually high number of daily infection cases detected in the city, Dr Bhupendra Patil, Medical Officer of Health (MOH), M West ward, says he has received an increasing number of applications for renting community halls, for weddings, engagements, and even birthday parties. "I asked my team to reject them. We cannot afford big, fat birthday celebrations at this point." As a rule, Patil takes down the names of all the persons attending a wedding ceremony, so that if somebody ends up getting infected, "we'll be able to trace guests ourselves rather than asking the infected person who all were present at the function." According to him, the trickiest events to handle are funerals. "For sentimental reasons, more people than the stipulated number turn up. And there's a culture of touching the body while paying last respects. If you try to stop them, they get offended. You have to be careful to not appear insensitive while trying to enforce rules."

Dr Bhupendra Patil

It's been a fortnight since Patil resumed duty after he and his family tested positive for COVID-19. He lost his father to the virus. "People don't realise that health workers and frontliners are experiencing a burnout. I have only taken two days of leave in six months. It's the same with the team. The common man needs to start taking responsibility for his and her own safety."

Unlike BMC and the Navi Mumbai Municipal Corporation (NMMC), the Kalyan-Dombivli Municipal Corporation (KDMC) continues to seal the entire wing of a building when a case is identified. "The numbers aren't dropping in this part of the city because of high density and tiny, congested apartments. We have imposed measures with the same level of strictness since March. Now people are fed up and don't want to listen," says Dr Pournima Dhake, medical officer, KDMC. Her department had started a campaign to raise awareness among shopkeepers and vegetable vendors after complaints that they were routinely seen flouting mask-wearing rules. "One of the officers then decided to test all street vendors in that ward, and only one turned out positive." Flummoxed as to why the cases were rising, the team then decided to test office goers from the same ward and 30 cases emerged. "With festivals coming up, we can't be lenient."

Dr Purnima Dhake

Instances of superspreading events abound, both in India and abroad. In February, in South Korea, a group of fitness instructors had attended a workshop, where they sweated it out in a small room. At least eight participants were infected, but didn't show symptoms or mild ones. Less than a month later, 112 people across 12 fitness facilities linked to a dance party had been infected in the region. Hong Kong's Lan Kwai Fong nightlife district triggered one of the biggest Coronavirus clusters in the city, infecting 106 bar patrons and staff. Closer home, a tourist from Italy was found to have infected over a dozen people in Jaipur, and a wedding afterparty in Dombivli led to 18 people getting infected.

Yaron Oz is a Rector at Tel Aviv University in Israel. He recently published his research on the super spreaders and the role they play in spreading COVID-19. According to Oz, the Coronavirus transmission more or less follows the 80/20 Pareto Principle, named after Italian economist Vilfredo Pareto, that states that 80 per cent of all infections come from just 20 per cent of the possible causes. "It is often assumed for simplicity that different individuals spread the disease more or less at the same infection rate. This leads to the estimate that 60-70 per cent of the population needs to contract the disease before herd immunity is reached.

Yaron Oz

However, the super spreaders change this drastically. The reason is that they tend to contract the disease quickly and infect many others." The R0 or the basic reproductive number signifies the number of people one infected person can pass the infection to, on an average. The R0 for COVID-19 is estimated to be between two and four. "Biologically, we do not really know. Socially we know, these are individuals who tend to have a large social network [who could possibly be super spreaders]. The more social encounters, the higher the chance to contract the disease."

Dr GiridharA Babu

Among the various COVID-19 suppression strategies adopted by countries, the one by Japan has been lauded despite allegations that the number of infections in the country were fudged and kept low to keep the Tokyo Olympic Games on schedule. Interestingly, Japan did not impose a lockdown. "Their public health response emphasised on changing behaviour patterns and instructed individuals to avoid the Three Cs: closed spaces, crowded places, and close-contact settings, which is key to controlling the spread," says professor Dr Giridhara R Babu, Head of Lifecourse Epidemiology at the Public Health Foundation of India, Bengaluru.

In a Twitter thread, cell biologist Hironori Funabiki cites how cases were reported where a single infected patient transmitted the infection to multiple persons in areas such as gyms, mahjong rooms, guest houses at ski resorts, and air-tight provisional tents. The team set the priority to suppress SSEs, and urged people to avoid closed spaces with poor ventilation, crowded with many people, full of conversations and vocalisation in close proximity (within arm's reach of one another).

An additional explanation for Japan's outlier status is being attributed to the cultural practice of mask-wearing without a mandate. "In Japan, thanks to widespread severe allergies to cedar pollen, it has been ordinary for Japanese to wear masks. Another cultural point is related to anthropologist Ruth Benedict's idea of Western guilt cultures and Japanese shame culture. Few speak in buses and trains in Japan. Cell phone talking is strictly discouraged. Many local habitual rules must be obeyed in public," writes Funabiki.

A man with a face mask walks along a street in Tokyo. Willingness to wear a mask is a key factor in control of infections in Japan, say experts. In fact, this month, the authorities have loosened voluntary restrictions on bars and restaurants and launched the Go To Eat campaign aimed at reviving the restaurant industry by providing subsidies to consumers. PIC/GETTY IMAGES

Babu says the focus should be on super spreader events, rather than on people. "In my opinion, there are no super spreader persons, but there are super spreader events. The Metro or local train is a classic example. You have a large number of people in an enclosed space with little room to breathe. So, if somebody is infected, you are creating a mini SSE within each coach. Unless everybody is wearing masks inside, there's no way that infection can be prevented." The task of controlling SSEs is a process, he thinks. "Japan did well at the beginning and later there was an increase in cases. Similarly, with South Korea. It's not like a test-match that ends after five days. It [effort] has to be ongoing."

Although there have been reports of SSEs across the country, some get more attention than others. "There was a case at a factory in Nanjangud where a lot of workers got infected and similarly, at the Jindal factory in Bellary. This hardly received any media attention. We only remember the Tablighi Jamaat congregation that took place in Delhi," he adds.

Oz believes that Israel's current model of a complete lockdown may not be effective in the long run because of its disastrous economic and social consequences. He says once out of the lockdown, a much cleverer policy should be implemented that takes into account the heterogeneous structure of the society and the spread of the disease.

Scientists have suggested that at least 70 percent of a given population must be immune to achieve herd immunity. But, according to Oz, the possibility might be closer than we thought. "Let's say, 20-30 per cent of the population gets immune to the virus, it is likely that in many places it [herd immunity] will reach before the vaccine arrives." He further adds that the SSE phenomena suggests that we do not need to offer vaccination to 60 to 70 per cent of the population in order to reach immunity, "but actually a smaller fraction".

Strategies that worked

Sweden Swedes went into self-lockdown. The country adopted a 'light touch' policy and only issued advice to its citizens to practice social distancing and personal hygiene. The country's 10 million people were asked to work from home if possible, which most followed. Officials said they trust in the good sense of Swedes to keep their distance and wash their hands.

Pakistan Our neighbour is interestingly earning rave reviews for its COVID-19 control strategy. The Medical Microbiology and Infectious Diseases Society Pakistan (MMIDSP) credited the strategy of "smart lockdowns", based on inputs from leading infectious diseases experts in the public and private sectors. Due to economic losses, the country had begun reopening some factories in early April and has since been gradually easing curbs.

Japan To suppress SSEs, people were urged to avoid closed spaces with poor ventilation, crowded with many people, full of conversations and vocalisation in close proximity (within arm's reach of one another). Due to widespread allergy to cedar pollen, it is ordinary for the Japanese to wear masks anyway.

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