Coronavirus of Wuhan (2019-nCoV); What Should We Know?
You already heard about the new coronavirus infection that broke out in Wuhan in Hubei Province of China. This novel type of coronavirus has been designated as 2019-nCoV (2019 Novel Coronavirus). It has infected about 4,000 people so far, with 106 confirmed deaths, including a medical doctor in China who has been treating infected patients. Let us examine what this coronavirus is and how it differs from the 2003 breakout of SARS that broke out in China.
Both SARS (Severe Acute Respiratory Syndrome) of 2003 and the current Coronavirus of Wuhan belong to the same class of viruses. Both are also zoonotic diseases, means diseases that spread from animals to humans. Both SARS and 2019-nCoV originated from bats and spread to humans via other animals. Both spread by air (cough and sneezes) and cause flu or pneumonia-like symptoms. However, these two viral diseases differ from each other with respect to the speed of spread and virulence or causing fatality. SARS spread rather slowly, but caused higher mortality (9.6%) as compared to the 2019-nCoV infection which has been spreading rapidly but caused only about 3% mortality so far. Of course, at the time of break out of SARS in November 2002, the Chinese authorities kept it secret and did not inform the World Health Organization (WHO) until February 2003, and so the viral genome or genetic composition was not published until April 2003. By that time, despite its slow spread, SARS managed to reach to 29 countries, thus qualifying as a pandemic. The other Coronavirus infection of recent years that could reach 28 countries is MERS (Middle East Respiratory Syndrome) of 2012, which originated in Saudi Arabia, and had a mortality of 34.4%. MERS virus also is zoonotic origin, with the virus being harbored in dromedary camels which have one hump and used for racing. The other two types of deadly viral disease of recent times, Ebola and Nipah are also zoonotic origin, transmitted from monkeys and fruit bats to humans, respectively. Both were deadly, with a mortality rate of 40% for Ebola and 77% for Nipah. However, thanks to their mode of spread (contaminated blood or direct contact with an infected patient), they were confined to only a few countries (9 for Ebola and 2 for Nipah). So, the ability of causing a wide spread infections (pandemic) and death (mortality) are not the same. Spread is related to how the disease is transmitted from person to person, air borne being rapid than blood borne. Mortality is dependent on how virulent or deadly the virus is.
Coming to the current Coronavirus of Wuhan, it is definitely less virulent causing only a few deaths, but it is spreading rapidly, despite the fact that Chinese authorities are quick to announce the outbreak to WHO. and took several emergency measures to contain the spread. So, even if the Coronavirus reaches the United States, we need not be worried too much. It may cause much fewer deaths than the usual flu season, which is between 12,000 to 60,000 per year in the USA. In other words, the current Coronavirus is not more deadly than the regular flu, although the news may sound scary to read and watch. One can take care of oneself by avoiding crowded places and restricting the air travel to the essentials, at least until the spread of Coronavirus is contained and authorities feel confident of that. One should wash hands frequently with soap for at least 20 seconds, and avoid touching strangers or even familiar persons if they appear sick. The people at highest risk for mortality due to Coronavirus infection are children, elderly persons, pregnant women and those who are immune compromised, meaning low immune power (e.g., HIV patients).
With regard to the question, why cannot we prevent zoonotic disease outbreaks like these ones? For millions of years, different types of viruses were “locked up” in different species of animals and human beings. They were multiplying and spreading among their designated host species. Humans became adepts in preventing and/or eradicating the viral diseases that specifically affect them, such as smallpox, polio, measles, influenza, hepatitis and others. In parallel, due to dwindling number of animal hosts, such as bats, birds, camels, monkeys etc., the viruses that were locked up in these species for millions of years were struggling and looking for other species as their new hosts. Naturally, they eye the humans, who are available in large numbers, and have no natural immunity to these viruses. In other words, by controlling and eradicating the viral diseases prevalent among themselves, the humans unwittingly invited the viruses from animals and birds. The animal and bird viruses must be looking for this type of chance to jump to humans via other animals for a long time. The wet markets of China, where live animals and birds are traded along with meats of different animals and seafood in congested shops, with the stall vendors coming very close to them, offer a suitable environment for these viruses to jump from their natural hosts to humans. Once they jump, the viruses need to mutate rapidly in order to develop the capacity to multiply and spread through the new type of host, the humans. These mutations create a barrier to develop vaccines within a short period of time. Because, the mutations may result in different types of stable organisms, depending on the environment and host defense mechanisms. Please keep in mind, the goal of the virus is just to survive, multiply and spread. Causing a disease in humans is not their goal. They just want to survive as many years as they can. Killing the host is suicidal for them as well. So, in order to achieve the goal of long-term survival, the zoonotic viruses may adopt a stable mutation that is less virulent, but more efficient in spreading, just like some strains of flu viruses. If this happens, as it did with SARS virus, there is no danger of fatalities. However, this does not happen always, as some viruses like to adopt a more virulent posture, depending on the prevalence of other deadly viruses in the host environment. For example, if there is prevalence of another virulent viral infection in humans where the new zoonotic virus infection broke, it is highly likely the latter will mutate to a more virulent strain in order to establish its own territory and spread among humans. In the hindsight, the fact that humans controlled or eradicated the classical viral diseases, such as smallpox, polio, measles etc., might have made the transmission of zoonotic diseases easier these days, apart from other factors. Whatever it may be, developing a vaccine for new zoonotic diseases is not easy and time consuming, as it requires identification of what mutant strain will prevail ultimately among humans. In view of these factors and others, scientists are still working on SARS vaccine. So, the best course of action now is taking the precautions seriously and preventing the chances of getting infected.
Contributed by: Bellamkonda K. Kishore, M.D., Ph.D., MBA