(With inputs from Dr Monica Vasudev)

916: Super spreader a must for becoming a hot spot of Coronavirus

Without a super spreader the cases in the country may die out of its own

Super spreader, is a term loosely used for people who infect a disproportionately large number of others, whether because of genetics, social habits or simply being in the wrong place at the wrong time.

Super spreader is a feature of nearly every outbreak. In fact, the primary case of every epidemic is a super spreader. China cases in Wuhan also might have started with a super spreader.

On average, each person infected with the new coronavirus passes it on to 2-3 other people. But this is only an average. Some people will go on to pass it to nobody while others may pass it on to far more.

The year 2015 saw a super spreading event wherein 82 people were infected from a single hospital patient with Middle East Respiratory Syndrome (MERS). Additionally, in the Ebola epidemic in West Africa, about 61% cases came from just a tiny handful of patients (3%).

Some just encounter far more people, either because of the nature of their job or where they live, and that means they can spread more of the disease, whether they themselves have symptoms. Then there are others who are "super-shedders". These people release unusually large amounts of virus (or other pathogen) from their bodies. As a result, anybody encountering them is more likely to become infected.

Hospitals treating SARS became a major center of super-spreading as the sickest patients were also the most infectious and they encountered lots of healthcare workers.

It plays a big role at the outset of any outbreak, when the virus is trying to establish itself. When it enters the first patient, the disease might fizzle out before it can cause a large outbreak. However, if it succeeds in quickly finding its way into a super spreader, then it gives the outbreak a boost. The same rules apply when cases are imported into other countries.

"Typhoid Mary", the Irish cook Mary Mallon (1869-1938), unknowingly passed on typhoid fever when she had no symptoms and spent decades in exile and forced quarantine.

An HIV person co-infected with STI becomes a super spreader. A heterosexual man co-infected with HIV, hepatitis C virus, and herpes simplex 2 virus has unusually high semen HIV RNA levels.

20/80 rule, a small percentage of individuals within any population controls most transmission events.

A study from Israel has found that the so-called super spreaders in Israel have been unusually potent: With many viruses, 20% of patients are often responsible for 80% of cases; however, the Israeli coronavirus data showed that only 5% of patients accounted for spreading the disease to 80% of those infected.

Several reports have shown the microbe’s affinity for density. The virus has been shown to spread easily in nursing homes, prisons, cruise ships and meatpacking plants. These are places where many people are living or working close together. A CDC report has described how a choir practice in Washington state in March became a super spreader event when one sick person infected nearly 52 others.

Differentiating those who are more infectious from those less infectious could make a huge difference in the ease and speed with which an outbreak is contained. If the infected person is a super spreader, contact tracing is especially important. But if the infected person is the opposite of a super spreader, someone who does not transmit the virus, contact tracing can be a wasted effort.

There has to be a link between people for transmission to take place. A link is necessary but not sufficient and the second factor is how infectious a person is.

It can be easy to wrongly attribute multiple infections to an individual, thus possibly exposing the person to public attack, when the spread has nothing to do with the person’s infectiousness. If you are the first person in a crowded room to get infected and if the disease is easily spread, you will look like a super spreader. Anyone present in that room could have had the same effect. Unfortunately, you were just the first in line.

Super spreading events may involve people with symptoms that linger but who are not sick enough to stay home.

Or they could involve infected people who shed an unusual amount of virus, a factor not well studied, that might be due to variations in the amount of virus in the aerosol droplets from a patient’s cough or the amount of infectious virus in feces.

No matter what the cause, public health measures, such as avoiding crowded places, and cough hygiene, can prevent a super spreading event.

Medical history is full of reports of super spreading in outbreaks of parasitic disease, tuberculosis, measles and other illness. There is Mary Mallon, a cook better known as Typhoid Mary, who spread typhoid fever to more than 50 people in the early years of the twentieth century. She herself was not ill but was asymptomatic — silently infected with typhoid.

1. China first case looks like it was a super spreader.
2. The cases in Diamond Princess ship - was a case of super spreader focal outbreak.
3. The lady in South Korea cult church was a super spreader. There were 28 cases of the coronavirus in South Korea on Feb. 13. Four days passed without a new confirmed case. The President predicted that the outbreak would soon disappear, while the Prime Minister assured that it was OK not to wear surgical masks outdoors. They probably missed the super spreader possibility. The virus was rapidly spreading through a large, secretive churchin Daegu, with the presence of a super spreader, where it has since developed into the largest epidemic of the coronavirus outside China, with 1,766 cases, including 13 deaths. The President then faced a political backlash over his response as the number of cases continued to climb.
4. Iran outbreak is possibly from a super spreader.

Possibilities of finding super spreaders

1. Person with lower respiratory coronavirus illness
2. Person with coronavirus pneumonia
3. Critically ill or terminal coronavirus infected patients
4. Immunocompromised persons with coronavirus infection
5. Person who has not suffered from any other corona illness in past with non-virulent strains
6. Rapidly developing corona illness with very short incubation period
7. Direct exposure to a super spreader compared to secondary or tertiary cases
8. Co-infection with another pathogen
9. Delayed identification and hospital admission of a super spreader

Summary

1. Low grade transmission: Through a spreader
2. High grade transmission: through a super spreader; usually will end up with community spread.

Virus does not spread easily from contaminated surfaces or animals, revised CDC website state

The coronavirus spreads from person to person and not easily from a contaminated surface.

The revised guidance states, “The virus spreads easily between people.” It also states that the coronavirus is spreading easily and sustainably between people.

It made another major change to its website, where it stated the sources that are not major risks. Under the new heading “The virus does not spread easily in other ways,” the agency clarifies that touching contaminated objects or surfaces does not seem to be a significant mode of transmission. The same holds true for exposure to infected animals.

Dr KK Aggarwal

President CMAAO, HCFI, Past National President IMA, Chief Editor Medtalks