COVID-19

COVID-19 is a disease that results from infection with SARS-CoV-2, a coronavirus that apparently first infected human populations in Wuhan in the People’s Republic of China towards the end of 2019. The disease was first described as an atypical ‘viral pneumonia’, and by January 2020, the infectious agent had been identified as a novel coronavirus. The origin of the infectious agent is uncertain: the current consensus is that it probably originated in bats, and that a novel mutated form of the virus, in which a spontaneous mutation had enabled the virus to infect humans, may have infected humans through interactions between live bats and people at a wild food market in Wuhan.

On 13 January 2020, the World Health Organisation (WHO) published protocols to diagnose infections using real time RT-PCR (reverse transcriptase polymerase chain reaction). https://www.who.int/docs/default-source/coronaviruse/wuhan-virus-assay-v1991527e5122341d99287a1b17c111902.pdf?sfvrsn=d381fc88_2 On January 22, 2020, The China National Health Commission reported the details of the first 17 deaths attributed to the new coronavirus: 13 males and 4 females, with a median age of 75 years.

By late January 2020, it was clear that the disease was being transmitted by person-to-person contact; the disease was rapidly spreading throughout Hubei Province, where Wuhan is located, and cases had been reported in several other countries, apparently attributable to travel from Wuhan. Accordingly, on January 30, the WHO declared the coronavirus outbreak a Global Public Health Emergency. (https://www.who.int/emergencies/diseases/novel-coronavirus-2019)

By March 2020, deaths had been attributed to it. The disease had already spread to several other countries, and on March 11th 2020 the WHO declared the coronavirus outbreak to be a pandemic. Soon virtually every country in the world was experiencing cases of the disease.

In China, strong measures were taken in early 2020 to control the outbreak. Movement in and out of Hubei Province was controlled very strictly, and severe restrictions were placed on social contacts within the Province. This containment policy was combined with a rigorous policy of contact tracing and isolation, and enforcement of mask wearing and other precautions. These measures effectively suppressed the outbreak in China.

By December 2020, more than 66 million cases of Covid-19 had been reported globally; it seems likely that this is a considerable underestimate as many cases are asymptomatic, and many others with symptoms were never tested.

Symptoms

The median incubation period for COVID-19 is estimated to be 4-5 days after exposure, but incubation periods of up to 14 days have been reported in exceptional cases The spectrum of illness ranges from asymptomatic infection to severe pneumonia with acute respiratory distress syndrome and death. Of about 70,000 persons with COVID-19 in China, 81% cases were classed as mild, with no pneumonia or mild pneumonia, 14% as severe (defined as dyspnea, respiratory frequency ≥30 breaths/min, saturation of oxygen ≤93%, a ratio of arterial partial pressure of oxygen to fraction of inspired oxygen [PaO2/FiO2] <300 mm Hg, and/or lung infiltrates >50% within 24 to 48 hours), and 5% as critical (respiratory failure, septic shock, and/or multiorgan dysfunction or failure).

In a report on more than 370,000 confirmed COVID-19 cases with reported symptoms in the USA, 70% of patients experienced fever, cough, or shortness of breath, 36% had muscle aches, and 34% reported headaches.3 Other reported symptoms have included, diarrhea, dizziness, rhinorrhea, anosmia, dysgeusia, sore throat, abdominal pain, anorexia, and vomiting.

Mortality

More than 1.5 million deaths had been attributed to Covid-19 by December 2020. There is considerable uncertainty about this number. Mortality from Covid-19 increases sharply with age, and is exacerbated by a range of comorbidities including obesity and diabetes. Accordingly some have noted that dying with covid-19 does not always mean the same as dying from covid-19. This factor might overestimate the rate of death due to covid-19, conversely, in some settings there is considerable underdiagnosis of covid-19 related death. There has also been concern that the measures taken to contain outbreaks of covid-19 may have affected the rate of deaths from other causes. On the one hand, measures taken to limit transmission of covid-19 are also likely, for example, to have been effective in limiting transmission of influenza, reducing the death rate from this disease. Conversely, effects on mental health of social isolation, and reduced access to health care may have increased deaths from diversity of other causes. Given these uncertainties, some believe that the most reliable estimate of deaths caused by covid-19 come from measures of ‘excess deaths’ – the total number of recorded deaths in a region compared to historical data on the expected number of deaths.

The UK is one of the countries that has been hardest hit by the Covid-19 pandemic.

COVID-19 most commonly spreads during close contact • People who are physically near (within 6 feet) a person with COVID-19 or have direct contact with that person are at greatest risk of infection. • When people with COVID-19 cough, sneeze, sing, talk, or breathe they produce respiratory droplets. These droplets can range in size from larger droplets (some of which are visible) to smaller droplets. Small droplets can also form particles when they dry very quickly in the airstream. • Infections occur mainly through exposure to respiratory droplets when a person is in close contact with someone who has COVID-19. • Respiratory droplets cause infection when they are inhaled or deposited on mucous membranes, such as those that line the inside of the nose and mouth. https://www.cdc.gov/coronavirus/2019-ncov/more/scientific-brief-sars-cov-2.html