As my friend said, maybe you shouldn’t eat things that have mothers. Here in the Comox Valley, I am brushing up on my East Asian geography and reminding myself of the epidemiological terms I learned over forty years ago. The new coronavirus (COVID-19) epidemic has got my attention.
The etymology of Epidemiology comes from three Greek words epi, meaning on or upon, demos, meaning people, and logos, meaning the study of – the study of what befalls a population.
As you all know by now, this Epidemic started because a novel agent (COVID-19) or a change in the virulence of an existing virus and susceptible hosts (humans via an intermediary species via bats) were present in adequate numbers. The outbreak of the flu-like symptoms caused by the RNA virus, COVID-19 in Wuhan, Hubai China is linked to a large seafood and a live animal market, suggesting animal-to-person spread of the virus similar to SARS and MERS
The virus is transmitted by direct contact or coughing and sneezing and the pathogenicity of the agent is severe enough to cause an infection rate that is high enough for further human-to-human propagation of the virus occurs. Each infected person can spread the virus to three or four other others.
There are many unknowns. Can surfaces that are contaminated by infected people can infect others? How long can the virus stay infectious or can it be transmitted by other bodily fluids for example vomit, urine, feces or breastmilk? Is it transmitted by droplet nuclei? These are the residue of dried droplets of infectious agents that remain suspended in air for longer periods or blown over greater distances than the wet droplets from coughing or sneezing.
The calculations for the risk of getting the virus or the attack rate are confounded by the unknown number of minimally symptomatic persons or those who are asymptomatic (a carrier) or convalescent – those who have had the virus but may still be spreading it.
The incubation or latency period, the time interval from exposure to the virus to the onset of symptoms is thought to be less than fourteen days based on information from the previous coronavirus infections, SARS and MERS.
COVID-19 may be asymptomatic or only cause mild symptoms. Mild symptoms may occur in as high as 80% of those infected but it is hard to put numbers on it – the data are changing hourly and there is no accurate denominator. (the true number of the uninfected) The severe flu-like symptoms or pneumonia, respiratory failure, other multiple organ failures and death seem to be occurring at rates of less than 20%.
The transmission rates are unknown (see infection rate) but it makes sense that the sickest people would be most contagious – shedding the most virus. The virulence is unknown as health care centres are only seeing the sickest people. Critical to understanding both transmissibility and virulence is knowing definitively who is infected with COVID-19 and what if any other viral co-infections are present.
Based on overt data, the mortality is around 2-3% compared to about 0.1% for the flu. Death rates are higher in older and sicker people with other chronic diseases. The death rate may be a lot lower if there is a large undiagnosed population with mild or no symptoms.
Accurate testing for the virus requires enough high quality RNA sampling kits, appropriate swabbing of mouth and nose, storage, transport and analysis of the samples. These are all difficult variables to manage given the wide geographic spread of and high numbers of people possibly affected.
Symptomatic or COVID-19 positive patients are placed in isolation to prevent human-to-human contact between symptomatic and asymptomatic persons. Isolation is maintained until viral samples are negative.
Quarantine is the isolation of potentially exposed but currently asymptomatic persons. The quarantining of a mixture of possibly asymptomatic but infected persons and uninfected persons in the setting of a cruise ship probably increased the risk of spreading the virus despite all the measures taken.
Similarly, mandatory quarantine measures may have had the effect of widely transmitting the virus as the asymptomatic or mildly symptomatic persons, but also infectious chose to evacuate themselves further spreading the disease. There is nothing delicate about the imposition of quarantine restrictions and the martial measures required to maintain them. Smartphones are being used by local authorities to track the activities of quarantined Chinese citizens.
For COVID-19, the duration of quarantine is 14 days from the last date of exposure because 14 days is the longest incubation period seen for similar coronaviruses like SARS and MERS.
Immunity to 2019-nCoV infection is not yet understood. Patients with the similar but more higher mortality MERS-CoV infection are unlikely to be re-infected shortly after they recover. It is not yet known whether similar immune protection will be observed for patients with 2019-nCoV infection.
There are no approved antivirals for the treatment of COVID-19 but trials are in progress with a combination of the antiviral agents, lopinavir and ritonavir.
And in our global village, when does an epidemic become a pandemic – a large proportion of the population affected over geographically separated countries? As I look at the distribution maps in the New York Times, it seems that the “unaffected countries” are also the ones with the poorest health care resources to report or manage affected persons.
It has been the best of times and the worst of times with great cooperation of open source information that resulted in rapid genomic sequencing, on-going vaccine development and clinical trials of antiviral therapies. But then there is also the misinformation, racism, and the economic fallouts from cancelled business ventures, tourism, manufacturing and interrupted supply chains for all sorts of products including essential medical supplies.
Last week, when I tried to buy some alcohol-based hand sanitizer at a big chain drug store, I was told that they were sold out. Even the local pharmacy has This global event has reached my doorstep. A friend supposed that people are either stock-piling supplies or sending them to relatives or friends in need.
Things are changing so rapidly. I am finding the New York Times coverage, the CDC sites and this Lancet hub-spot most useful for reliable and current information.
But please try to keep perspective. Influenzas A and B have already caused more deaths this season that this new coronavirus. The CDC estimates that so far this season there have been at least 26 million flu illnesses, 250,000 hospitalizations and 14,000 deaths from the flu. Get vaccinated annually!
And while you are at it, you may want to review this video of the CDC recommendations for hand hygiene. Remember that when properly used simple soap and water (adequate water availability is a huge issue in the developing world) are more effective than hand sanitizer.