Coronavirus could spread explosively, tight control needed
The coronavirus may be taking a higher toll of life than we thought, say scientists, in a new study published on January 30, 2020, in The Lancet. But another startling new study based on mathematical modeling, published in the same journal, predicts that almost 76,000 people may have acquired the infection in Wuhan city, and that multiple epidemics in major connected cities inside and outside China may already be brewing. Yet the death rate is markedly low, in this case.
The novel coronavirus 2019 (2019-nCov) that caused an outbreak in Wuhan city, Hubei province, China, has now spread to 25 countries including ones as far away as Australia and the USA, revealing, among other things, the power of globalization to spread other things than technology. At present, over 425 people havedied from the infection.
The study
The researchers in the first study looked at a single group of people who had been treated in an isolation facility at Jinyintan hospital over the period between January 1 and January 20, 2020. All of them had originally been seen and treated at other hospitals in Wuhan. Over 2 out of 3 people in this group were men. Their ages varied from 21 to 82 years.
About 50 percent of the group had been exposed to the Huanan Seafood Wholesale Market, the place where the initial animal-to-human spread is thought to have occurred. The vast majority were working at the market. Only 2 were shoppers.
Huanan seafood market. Image Credit: Pikitia / Shutterstock
Mortality – low or high?
In this study, 11 patients died, and 32 were discharged. Obviously, the mortality rate goes far above the early estimate of 2 to 3 percent supplied by the World Health Organization and the Centers for Disease Control (CDC). Moreover, the rate of death might go higher since most patients are still in hospital. The cause of death is acute respiratory distress syndrome caused by severe inflammation of the lungs, septic shock caused by overwhelming bacterial presence in the circulation leading to the fatal breakdown of multiple organs simultaneously.
The earlier epidemic caused by the SARS (severe acute respiratory syndrome) had a mortality rate of 10 percent but the MERS (Middle East respiratory syndrome) claimed the lives of 34% of its victims.
The current virus appeared to spread much more easily and quickly than the above viruses, but to be less deadly. Many experts in public health think the current findings don’t change that view. One major reason: the mortality reported in this group is that of a selected group of patients who might have been referred to that hospital simply because they were already sicker than others. And therefore, according to US epidemiologist Eric Feigl-Ding, “The total per cent case fatality is likely lower because (a) lot of infected patients with less severe symptoms might not be in this hospital pool.”
A second telling reason for scepticism is the small number of the sample. And thirdly, over 30 percent of patients were discharged within 2 weeks, leading, reasonably enough, to the assumption that they were recovered.
High-risk group
Over two-thirds of patients were men, as with the earlier SARS and MERS epidemics. The researchers say: “The reduced susceptibility of females to viral infections could be attributed to the protection from X chromosome and sex hormones, which play an important role in innate and adaptive immunity.” In other words, women just don’t get sick with this virus as easily as men do, it appears.
Again, about half of these patients were also suffering from chronic disease, such as heart disease and diabetes. Some, including the first two patients to die, were healthy but had a history of long-term smoking.
In short, the risk of infection with the 2019-nCov virus is highest in older men who have existing health problems. However, at least 5 people who were healthy and only in their fifties, and one who was only 36, have died of this infection, and the reasons are still not clear.
Modeling research shows high case load
Over 20,000 people have now caught the virus. All the deaths reported so far have been in China. The WHO has declared this a public health emergency of international concern (PHEIC. This includes, in part, answering 2 or more of the following questions in the affirmative:
- Is the public health impact of the event serious?
- Is the event unusual or unexpected?
- Is there a significant risk for international spread?
- Is there a significant risk for international travel or trade restrictions?
The modeling study was carried out against this background, because of the need to know how big the epidemic might eventually become, and how it might spread within and beyond China.
It took into account the number of confirmed cases, the extent of travel from Wuhan both inside and out of China, the time taken by one infected person to infect another (assuming it is the same as that of the SARS epidemic.
The researchers also adjusted for the likely effect of various public health interventions that were made after January 2020.
The startling figure of 76,000 infected individuals in Wuhan came from the assumption that in the early days each infected person might have spread it to an average of 2-3 others, and the size of the epidemic consequently doubled every 6.4 days. On the brighter side, the case fatality percent is far smaller than even 2 percent, in this scenario. However, with a huge number of cases, even a low fatality rate can cause many hundreds of deaths, as with the annual flu epidemic in the USA.
Reasons for high case number estimates
The modeled estimates far exceed the number of confirmed cases. Researcher Gabriel Leung says, “Not everyone who is infected with 2019-nCoV would require or seek medical attention. During the urgent demands of a rapidly expanding epidemic of a completely new virus, especially when system capacity is getting overwhelmed, some of those infected may be undercounted in the official register.”
Why should this happen? He explains, “There is a time lag between infection and symptom onset, delays in infected persons coming to medical attention, and time taken to confirm cases by laboratory testing, which could all affect overall recording and reporting.”
The study emphasizes that on the basis of its modeling, many large cities in China could already have imported enough cases to have their own local epidemics break out a couple of weeks from the Wuhan epidemic. These cities include Guangzhou (modeling estimate: 111 cases), Beijing (113), Shanghai (98), and Shenzhen (80). Over 50% of people traveling out of China leave from these cities.
Major overseas cities with larger volumes of traffic across the Chinese borders could also become new centers of the infection. The reason is that unlike the SARS virus, the 2019-nCov apparently takes up to 8 days before causing the first symptoms. Thus, infected but asymptomatic people traveling freely between these countries could spread it rapidly far and wide.
Need for strict control measures
Researchers show that if the virus spread could be contained by 25%, predicted local epidemics could be slower and smaller. And if it is cut by half, the epidemic will become a slowly growing one. For this to happen, tight and effective public health measures, including harsh quarantine of affected areas, must be immediately put implemented to keep the epidemic confined to small areas in these cities. The study does not show, of course, how or if this can be done.
Co-author Kathy Leung outlines additional measures to prevent further rapid spread: “Strategies to drastically reduce within-population contact by cancelling mass gatherings, school closures, and introducing work-from-home arrangements could contain the spread of infection so that the first imported cases, or even early local transmission, does not result in large epidemics outside Wuhan.”
Or of course, the epidemic could just die down slowly instead. But will it? Nobody knows yet.
Measures to manage this scenario
Leung calls attention to the importance of preventive and preparedness measures: “Based on our estimates, we would strongly urge authorities worldwide that preparedness plans and mitigation interventions should be readied for quick deployment, including securing supplies of test reagents, drugs, personal protective equipment, hospital supplies, and above all human resources, especially in cities with close ties with Wuhan and other major Chinese cities.”
Journal reference:
Nowcasting and forecasting the potential domestic and international spread of the 2019-nCoV outbreak originating in Wuhan, China: a modelling study Wu, Joseph T et al. The Lancet, https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)30260-9/fulltext
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