Coronavirus – the science: The search for ‘patient zero’

Edition 1: Researchers assessing number of undiagnosed and how infectious these people are

This is the first in a series of regular updates from Irish Times Environment and Science Editor Kevin O’Sullivan on scientific initiatives and developments in relation to the coronavirus:

The search for ‘patient zero’

There is an intense ongoing investigation to find out exactly when Covid-19 emerged in humans. It’s important to identify how epidemics emerge, not least the current pandemic, and especially how it is spread. As suspected, it was in circulation a lot earlier than initially indicated.

A 55-year-old individual from Hubei province in China may have been the first person to have contracted Covid-19, according to the South China Morning Post. This dates back to November 17th, more than a month earlier than doctors noted cases in Wuhan in late December.

Authorities suspected the virus stemmed from something sold at a “wet (seafood) market” in the city. It’s now clear some infected people had no connection to that location. That included one of the earliest cases from December 1st; researchers reported in The Lancet.


Scientists now suspect SARS-CoV-2 (its medical name) originated in a bat and somehow hopped to another animal, possibly the pangolin, which then passed it on to humans. It is now spreading between people without any animal intermediary.

If they can find the earliest cases, they may be able to confirm the animal host where the virus lurks. Even with this November 17th case identified, doctors can’t be certain the individual is “patient zero”, the first to have been infected. There’s every chance even earlier cases will be found.

The undetected

A report just published in Science is among the first to address two of the most pressing questions about the Coronavirus pandemic: How many people are walking around with unrecognised infections, and how infectious are they?

Scientists tracking the coronavirus spread believe for every confirmed case, there are most likely another five to 10 people in the community with undetected infections.

These often-milder cases are, on average, about half as infectious as confirmed ones, but are responsible for nearly 80 per cent of new cases, according to research published in Science – it is based on data from China.

The researchers modelled the virus's natural spread there before the government instituted a travel ban and an aggressive testing policy. During that time from December 2019 through late January about six in seven cases went undetected. That situation is similar to where in Europe and the US tests are not widely available, they conclude.

"If we have 3,500 confirmed cases in the US, you might be looking at 35,000 in reality," Jeffrey Shaman, an epidemiologist at Columbia University, told the New York Times – latest Irish predictions are we may reach 15,000 by the end of March.

Covid-19 watch

The World Health Organisation regularly updates on cases and associated data. That is then fed into models all over the world designed to predict what's likely to unfold. Critically, they inform actions in an attempt to "flatten the curve" of accelerating cases.

The "confirmed cases" curve revealed Ireland's early rise in cases was outpacing those in other countries already in the throes of a health crisis, most notably Italy and South Korea. But confirmed cases, however, may be relative to different rates of testing in different countries. These numbers will also be shaped by how actively testing is done. Ireland is in "rapid scale up of tests" phase.

What forced a change of tack in the UK on Monday was new data on the impact of Italy's out-of-control epidemic on its health service where 30 per cent of hospitalised patients had to be admitted to intensive care. Modellers at Imperial College and the London School of Hygiene and Tropical Medicine who advise government crunched those numbers – and the death toll and pressure on the NHS that came out were unacceptable.

The mitigation strategy the government had just announced would lead to 260,000 deaths. That would be not just deaths from the virus, but from other illnesses the NHS would be too hard-pressed to treat. Hence, measures were scaled up again – though not nearly as extensive as in Ireland.

Prof Liam Glynn of UL and Dr Mike O'Callghan provide a succinct update and Irish number crunch daily through #COVIDWATCHon Twitter. Their St Patrick's Day report reads: "Cases increasing (due to more testing) but our deaths very low SO FAR. WE CAN SAVE LIVES. Be a hero and play your part on Paddys day."

Three grounds for optimism

– Medical workers in Wuhan revealed smiles behind their masks to celebrate the closing of the last temporary hospital that was panic-built to accommodate the overflow of coronavirus patients in the city.

– Scientists at Erasmus Medical Centre in Rotterdam and Utrecht University have found an antibody against Covid-19 which could prove vital to producing antiviral medication against coronavirus. Professor of cell biology there Frank Grosveld (71) says he is keeping his cool: "I am too old to jump on a table."

– Doctors in India have been successful in treating coronavirus through a combination of four drugs (Lopinavir, Retonovir, Oseltamivir and Chlorphenamine). They are going to suggest this be applied globally.