Estimating the Real Number of COVID-19 Cases in Wuhan

The Coronavirus Likely infected over 200,000 by February 2020. I analyzed the First Four Months of the Coronavirus Outbreak using several University estimates to create a line graph.

Two years have passed since the coronavirus morphed from a local outbreak into a global pandemic. While the official number is over 50,000 several studies from researchers have concluded that the numbers during the initial outbreak are higher. By January 22nd the reported case numbers were a little over 200 while the University of Hong Kong estimates 62,468 or more were infected with the coronavirus. This discrepancy brings up two questions.

How many cases were in Wuhan during the initial outbreak?

What would it have looked like to local officials during the first four months of the outbreak that lead to a severe lockdown for 11 million people?

I’ll be using three different estimates to construct the cumulative case numbers and explain why those numbers are more accurate than the official reported tally. The data will be crowdsourced from the Hong Kong Institute of Virology, the University of San Diego, Northeastern University and the National Institute of Public Health.

Because most estimates for the first animal to human transmission range from mid-October through early December we’ll begin with a starting point of November 20th since there we’re no indications of excess number of deaths related to COVID until mid-December. By using confirmed estimates on key dates from these several sources we can calculate what the real numbers would have looked like from November 2019 through February 2020. Let’s start with the discrepancy in the numbers.

Inconsistent Numbers

On January 23rd, 2020, the city of Wuhan was placed under strict lockdown at the time when there were only 193 cases confirmed within the city of 11 million. And this lockdown occurred at the same time as two brand new hospitals were under construction on the outskirts of the city to support an additional 2,000 patients and finished within ten days. There were seven hospitals prior to these two new one’s being constructed. Because of limited data on how many hospital beds were in use for covid patients during the outbreak it could be anywhere from 250 patients to 500 per hospital (1,750 to 3,500). The only explanation for the addition of two new hospitals is a severe undercount in case numbers.

In order for two new hospitals to be built in Wuhan within ten days to handle two-thousand new patients, the remaining seven hospitals would likely be filled to capacity as some of these videos from the BBC indicate. Although the local government reported 6.51 beds per 1,000 patients that doesn’t give us an idea of how many were in intensive treatment during the initial outbreak. The Washington Post reported in early February hospitals in Wuhan were at the breaking point as coronavirus patients flooded hospitals delaying procedures for people who did not have covid, straining the system. Based on this information we believe the case numbers are much higher and spread quicker than my own state of Washington.

Comparison of King and Snohomish Counties, Washington and Wuhan, China

It’s important to compare this to another place where numbers are more accurate. The first official case in Washington state occurred on January 17th and it wasn’t until February 24th (36 days later) when cases started going up and up. This first cluster occurred in King and Snohomish counties which combined have a population density of around 666 people per square mile. Wuhan with a city of 11 million people has a population density of 3,279 people per square mile. Given this and a strong link between population density and coronavirus we will select November 20th as the starting point for the first case. With a population density five times greater than the Seattle area, it would have taken about a week or less before case numbers gradually increased before exploding exponentially.

Methodology

Although it remains unclear if the Huanan Seafood Market is the origin point, it is likely that the area between the market and Hankou Train Station is where the first super spreader event occurred. The area within the vicinity of the market was filled with hotels, restaurants, shops, grocery stores, and banks making it an ideal place to spread quickly. That combined with an open live animal market makes this place an ideal spot for a novel coronavirus to spread quickly to large groups of people.

While some estimates for the first zoonic nature of this virus varies (November 4th through November 17th) to ensure data quality we will put the official transmission date at a more conservative estimate of November 20th, 2019. With a population density per square five times higher than King and Snohomish Counties it would have started gradually climbing within a week before really ticking up by week two. To ensure accuracy of the data we’ll be using a low and a high estimate to show what the true number of coronavirus cases would have looked like with more accuracy. These numbers include symptomatic and asymptomatic individuals. We’ll be using the information from Northeastern University, University of San Diego, and the Hong Kong Institute of Virology to fill in the data between estimated case numbers.

Initial Outbreak (Nov 20th — Dec 11th)

Beginning from November 20th onward the number of cases would have started off slow before beginning to steadily rise and then really curve upwards. Most viral outbreaks such as these tend to follow an exponential growth formula. They start off with low numbers and then suddenly within days or weeks it shoots upwards. While there is still some uncertainty about whether the first documented case started in the Huanan Seafood Market, evidence suggests that this was most likely the first super spreader event as thousands traveled through this region inadvertently spreading the coronavirus. For every person that displayed symptoms one or two people were walking around asymptomatic spreading it further to other parts of the city.

To make matters worse it took an average of 23.3 days to confirm a diagnosis for the coronavirus in Wuhan. As CNN notes this would have severely hampered detection of the coronavirus for local officials who probably didn’t even realize a virus was circulating until late December. Although the exact origin will be up for debate for many years, what we do know is that by mid-December several hospitals received dozens of patients with pneumonia of unknown origin. By December 11th there were 70–200 people walking around infected with the coronavirus most of which went undetected (Frontline, 2020).

The Outbreak Spreads (Dec 11th — Dec 30th)

This period is where the virus really begins to take off with an estimated R-naught between 3.35 and 3.5 it spreads very quickly. By December 30th case numbers were estimated to be 2,300–4,000 as commuters spread further out from around the Huanan Seafood Market to other areas all over the city and beyond. The symptoms we’re beginning to be detected by doctors all over the region as they noticed antiviral treatment medications were not working for people they later dubbed as having ‘viral pneumonia of unknown’ origin.

By December 30th news of a new SARS-like virus were circulated among doctors in Wuhan including Li Wenliang an ophthalmologist at Wuhan Central Hospital. Wenliang was discussing with a group of four hundred doctors through the messaging service WeChat where he mentioned there were 7 cases of SARS were confirmed at Huanan Seafood Market. He warned his colleagues not to circulate the message outside the group and to tell their families to take precautions. But his message went viral through social media as did a report from local health commission barring doctors from releasing information about SARS to the public.

Dec 30th, 2019 — Jan 6th, 2020

By December 31st officials in Wuhan disclosed to the public that 27 cases of viral pneumonia were linked to the Huanan Seafood Market and that the market would be shut down the next day for sanitation. As workers began scooping up years of gunk from the drains thousands of people were walking around with little to no symptoms. By January 6th as many as 6,000–10,000 people were infected spreading the virus even further from the city center to the outskirts.

As this was spreading the national government barred them from releasing case totals to the public. Although most officials refused to speak with international reporters one person from the Central Hospital in Wuhan disclosed some details from early and mid-January. Around this period one person reported that the local hospital wouldn’t allow them to confirm a diagnosis suggesting the numbers align more with university estimates than with officially reported case numbers.

“I suspected there was human to human transmission around the 6th or 7th January…The respiratory department became full around the 9th or 10th. I realized this thing had become big. It was out of control.”

“Every day there were several hundred people with a fever. Hundreds every day. At the level of the hospital, we could not confirm a diagnosis. If you are talking about suspected cases at that time, there were already hundreds and hundreds. — Frontline Health Worker at Wuhan Central Hospital, Frontline 2021

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