Corona virus or SARS COV-2 or COVID- 19  came into light after it was reported that many patients in Wuhan China presented with an atypical pneumonia leading to severe acute respiratory disease and the disease was officially termed as COVID- 19 in February 2020. Ear, nose and throat  manifestations are this viral illness are very similar to common flu and it is very important to differentiate between the two .

Source and transmission:  Because of high genetic similarity with bat coronovirus it is presumed that the origin of COVID- 19 is bats and the transmission to human may involve other mammalian host. Human to human transmission is mainly through the respiratory droplets through coughing, sneezing and close contact with an infected patient. Other routes of transmission are also possible which include fomites and transmission of virus through contact with surface having virus as it was shown that virus can survive on solids for variable time.

General symptoms: Fever, dry cough, sore throat, headache and flu like disease with body aches are common with mild disease where as breathing difficulty with ARDS needing ventilatory support and diarrhoea are seen in advanced disease. Symptoms specific to Ear Nose and Throat  are loss of sense of smell and taste which is seen in around 40% of cases. Especially when combined with other symptoms and a travel history to a COVID- 19 affected area is highly specific of COVID- 19 disease.

Is it COVID- 19 or a normal flu?  Both illnesses can cause fever, cough, body aches, and sometimes vomiting and diarrhoea differentiating common flu from COVID- 19 is very difficult at time as the symptoms are often overlapping , however features like breathing difficulty with loss of sense of smell and taste are absent in common flu . The speed of transmission is an important point of difference between the two viruses. Influenza has a shorter median incubation period (the time from infection to appearance of symptoms) and a shorter serial interval (the time between successive cases) than COVID-19 virus. The serial interval for COVID-19 virus is estimated to be 5-6 days, while for influenza virus, the serial interval is 3 days. This means that influenza can spread faster than COVID-19.

Further, transmission in the first 3-5 days of illness, or potentially pre-symptomatic transmission –transmission of the virus before the appearance of symptoms – is a major driver of transmission for influenza. In contrast, while we are learning that there are people who can shed COVID-19 virus 24-48 hours prior to symptom onset, at present, this does not appear to be a major driver of transmission. The reproductive number – the number of secondary infections generated from one infected individual – is understood to be between 2 and 2.5 for COVID-19 virus, higher than for influenza. However, estimates for both COVID-19 and influenza viruses are very context and time-specific, making direct comparisons more difficult.

While the range of symptoms for the two viruses is similar, the fraction with severe disease appears to be different. For COVID-19, data to date suggest that 80% of infections are mild or asymptomatic, 15% are severe infection, requiring oxygen and 5% are critical infections, requiring ventilation. These fractions of severe and critical infection would be higher than what is observed for influenza infection.

Those most at risk for severe influenza infection are children, pregnant women, elderly, those with underlying chronic medical conditions and those who are immunosuppressed. For COVID-19, our current understanding is that older age and underlying conditions increase the risk for severe infection.

Mortality for COVID-19 appears higher than for influenza, especially seasonal influenza. While the true mortality of COVID-19 will take some time to fully understand, the data we have so far indicate that the crude mortality ratio (the number of reported deaths divided by the reported cases) is between 3-4%, the infection mortality rate (the number of reported deaths divided by the number of infections) will be lower. For seasonal influenza, mortality is usually well below 0.1%. However, mortality is to a large extent determined by access to and quality of health care.

Prevention:  till we get the vaccines for COVID-19, the three cornerstones of prevention are social distancing, hand hygiene and facial mask.

I have observed that people with moderate to severe hearing loss are at a disadvantage with using mask as the voice is often muffled and difficult to understand and lip reading is not possible.