Battling with viruses

The deadly outbreak of viral pneumonia in the city of Wuhan, China caused by a novel coronavirus designated 2019-nCoV by the World Health Organisation (WHO), also known as the Wuhan coronavirus, is again a great example of the constant battle between human and viruses. This new virus has already killed 106 people with almost 3,000 confirmed ill. By the end of Monday, a total of 4,515 cumulative confirmed cases of new pneumonia had been reported in Hubei, while 2,567 patients are hospitalised, with 563 in severe conditions and 127 in critical conditions as reported by the Hubei Provincial Health Commission on Tuesday. A total of 32,799 close contacts have been traced and under medical observation. Though the WHO declined to declare the virus as a global health emergency, it declared that the global risk from the deadly virus in China was "high". The risk was very high in China, high at the regional level and high at the global level as said by the UN health body.

All major Chinese New Year events have been cancelled along with all other large scale activities, including temple fairs. This has never happened in Chinese history. Lunar New Year holiday has been extended in a bid to prevent an infection whose spread accelerated around the globe. Since the virus is not yet under control, China has locked down 13 cities as aggressive steps to limit movement for millions of people who live in cities near the centre of the outbreak. More than 2,835 cases have been reported in 15 countries and territories. Overseas confirmed cases have been reported in Thailand (7), Japan (3), South Korea (3), the United States (3), Vietnam (2), Singapore (4), Malaysia (3), Nepal (1), France (3), Australia (4) and Sri Lanka (1). However, no positive case has been detected in India so far though samples of seven passengers have been sent to the ICMR-NIV Pune lab. Over 100 people have been kept under observation in Kerala and Maharashtra. The Prime Minister's Office reviewed India's preparedness to deal with any situation amid mounting global concern over rising cases in China.

Coronaviruses (CoVs) have long been considered inconsequential pathogens to humans causing the common cold. In the case of this new virus, the detailed information is not adequate even though the pathogen was identified relatively quickly. Genomic sequencing has shown that it is a positive-sense, single-stranded RNA coronavirus and its transmission from human to human is increasing. Without detailed information, particularly confirmation of the source, uncertainty will prevail about the virus that explores humans for the first time because once the virus starts replicating inside a cell, it can start to generate mutations that allow it to spread more efficiently and become more dangerous. Animals sold for food are the likely reservoir or intermediary for the virus because many of the first identified infected individuals were workers at the Huanan seafood wholesale market where poultry, snake, bats, and other farm animals were also sold. Earlier a market selling live animals for food was blamed in the severe acute respiratory syndrome epidemic in 2003.

China has been the epicenter of emerging and reemerging viral infections that continue to stir a global concern. In the last 20 years, China has witnessed several emerging viral diseases, including an avian influenza in 1997, the severe acute respiratory syndrome (SARS-CoV) in 2003, a severe fever with thrombocytopenia syndrome (SFTS) in 2010 and a Middle East respiratory syndrome coronavirus (MERS-CoV) in 2012. The two outbreaks of severe respiratory tract infection, caused by the SARS-CoV as a result of zoonotic CoVs crossing the species barrier, causing global epidemics with alarming morbidity and mortality. They jump from one species, where they went unnoticed, into humans. In 2003, the global SARS outbreak led to 774 deaths with 8,098 affected and cost the global economy billions of dollars. Effective public health measures brought the outbreak to an end. SARS is caused by a member of the coronavirus family of viruses (the same family that can cause the common cold). It is believed the 2003 epidemic started when the virus spread from small mammals in China.

In December 2019, novel coronavirus (2019-nCoV) has caused serious illness and death. The ultimate scope and effect of this outbreak is unclear at present as the situation is rapidly evolving. This brought CoVs global attention and highlighted the importance of controlling infectious pathogens at international borders. The viral pneumonia outbreak was not caused by SARS-CoV, MERS-CoV, influenza virus, or adenovirus as determined by laboratory tests. According to China's top virologist Yi Guan. the probable scale of a full outbreak can reach at least ten times that of SARS.

The coronavirinae family consists of four genera based on their genetic properties, including genus Alphacoronavirus, genus Betacoronavirus, genus Gammacoronavirus and genus Deltacoronavirus and are endemic globally and account for 10 to 30 per cent of upper respiratory tract infections in adults. Coronaviruses are ecologically diverse with the greatest variety seen in bats. They are the reservoirs for many of these viruses. Peridomestic mammals may serve as intermediate hosts, facilitating recombination and mutation events with expansion of genetic diversity. The coronavirus RNA genome (ranging from 26 to 32 kb) is the largest among all RNA viruses. Based on sound scientific evidences it is reported that the 2019‐nCoV was a recombinant virus between the bat coronavirus and an origin‐unknown coronavirus. The recombination occurred within the viral spike glycoprotein, which recognises the cell surface receptor. Snakes, particularly the Chinese krait and the Chinese cobra are the most probable wildlife animal reservoir for the 2019‐nCoV. The homologous recombination within the spike glycoprotein may contribute to cross‐species transmission from snake to humans. Homologous recombination is an important evolutionary force and homologous recombination occurred in many viruses, including Dengue virus, Human Immunodeficiency Virus, Hepatitis B Virus, Hepatitis C Virus and classical Swine Fever Virus. Currently, scientists believe it is either bats, snakes, or both and unregulated wild animal trading leaves areas vulnerable to virus spillover. Preliminary research suggested the virus was passed on to humans from snakes but government medical adviser Zhong Nanshan has also identified badgers and rats as possible sources.

With some viral diseases, the virus did not transmit before people developed symptoms. Such outbreaks are relatively easy to stop. Identify and isolate people who are sick and monitor anyone they came into contact with. In the case of this virus, people are infected but don't have any symptoms and do not initially feel sick. Thereby, people infected by this virus are still going to work or school, taking public transit, shopping in malls, or going to movies and pass the viruses to others. But stopping such 'symptomless spreaders' will make the job of the Chinese authorities much difficult to screen people infected by the virus.

Coronavirus can infect humans and many different animal species, including swine, cattle, horses, camels, cats, dogs, rodents, birds, bats, rabbits, ferrets, mink, snake, and other wildlife animals. Many coronavirus infections are subclinical. Reported symptoms of individuals infected by the new virus have included fever, fatigue, dry cough, shortness of breath and respiratory distress. Cases of severe infection can result in Pneumonia, kidney failure and death. WHO Director-General stated that a quarter of those infected experienced severe disease and that many of those who died had other conditions such as Hypertension, Diabetes or Cardiovascular disease that impaired their immune systems. A study reported that a majority of the patients were healthy before contracting the infection and that over a quarter of previously healthy individuals required intensive care. Among the majority of those hospitalised, vital signs were stable on admission and they had low white blood cells counts and low lymphocytes. Major cause of spreading this infection is the size and density of the population and close contact with animals, the reservoir of viruses. One research group has estimated the basic reproduction number of the virus appears to be between 3 and 5 meaning it typically infects 3 to 5 people per established infection. Other research groups have estimated the basic reproduction number to be between 1.4 and 3.8.

Right now, it has been recommended that travellers avoid all nonessential travel to China. In addition, the people who travel should practice certain health precautions like avoiding contact with people who are sick and practising good hand hygiene as there is no specific medicine to treat the infected patients without being panicked.

Most importantly at this point, it is impossible to know how severe it would be. Now there is emergent need to take preventive measure shortly otherwise there will be a pandemic. Global health policymakers must start planning to deal with the spread of the new virus. Such plans need to include far more aggressive efforts to develop a vaccine than have already been announced.

Dr Debapriya Mukherjee is a former Senior Scientist, Central Pollution Control Board. Views expressed are strictly personal