Most people will get a mild infection, but the pattern is clear in the most severe cases. So, what is going on, asks a BBC News report?
The report says all the information we have is coming from a massive study by the Chinese Centres of Disease Control. It looked at 44,000 people and showed 2.8% of infected men died compared with 1.7% of women. And 0.2% of children and teenagers died compared with nearly 15% of people over the age of 80.
The report says there are two ways of explaining the findings that women and children less likely to catch coronavirus. Either these groups are less likely to be infected in the first place, or their bodies are more able to cope with the virus. “Normally with new viruses circulating, everybody gets infected, that’s the important point,” says Dr Bharat Pankhania, from the University of Exeter. This is because there is no immunity to the virus as nobody has been exposed to it before.
Although in the very early stages of an outbreak children may be less likely to catch the virus. “One reason we haven’t seen so many cases in children is they are protected at the beginning of outbreaks, parents keep children away from the sick,” said Dr Nathalie MacDermott, from King’s College London.
Some may be surprised there’s a difference between men and women’s death rates from coronavirus, but, the report says, scientists aren’t. The same effect is seen in a wide range of infections including flu.
Part of the answer is men are generally in worse health than women due to lifestyle choices like smoking. “Smoking damages your lungs, that’s not going to be a winner,” says MacDermott. This may be a particular problem in the China where estimates suggest 52% of men smoke compared with just 3% of women.
But there are also differences in the way the immune systems of men and women respond to infection. “Women have intrinsically different immune responses to men, women are more likely to suffer from auto-immune diseases and there is good evidence that women produce better antibodies to vaccines against flu,” says Professor Paul Hunter, from the University of East Anglia.
The UK government says there is “no obvious sign” that pregnant women are more likely to be severely affected by the coronavirus. , but some experts have raised doubts. Pregnancy weakens the immune system and pregnant women are more likely to die from flu than non-pregnant women of the same age.
There is very limited information on the symptoms of Covid-19 in children, but they appear to be mild – fever, runny nose and a cough. “People tend to get more ill at the extremes of age as they have lower resilience.”
There have been some cases with more severe complications. Those with other health problems, such as a weakened immune system or severe asthma, will be at greater risk. But overall the virus appears to be milder in children.
Background: An outbreak of 2019 novel coronavirus diseases (COVID-19) in Wuhan, Hubei Province, China has spread quickly nationwide. Here, we report results of a descriptive, exploratory analysis of all cases diagnosed as of February 11, 2020.
Methods: All COVID-19 cases reported through February 11, 2020 were extracted from China’s Infectious Disease Information System. Analyses included the following: 1) summary of patient characteristics; 2) examination of age distributions and sex ratios; 3) calculation of case fatality and mortality rates; 4) geo-temporal analysis of viral spread; 5) epidemiological curve construction; and 6) subgroup analysis.
Results: A total of 72,314 patient records—44,672 (61.8%) confirmed cases, 16,186 (22.4%) suspected cases, 10,567 (14.6%) clinically diagnosed cases (Hubei Province only), and 889 asymptomatic cases (1.2%)—contributed data for the analysis. Among confirmed cases, most were aged 30–79 years (86.6%), diagnosed in Hubei (74.7%), and considered mild (80.9%). A total of 1,023 deaths occurred among confirmed cases for an overall case fatality rate of 2.3%. The COVID-19 spread outward from Hubei Province sometime after December 2019, and by February 11, 2020, 1,386 counties across all 31 provinces were affected. The epidemic curve of onset of symptoms peaked around January 23–26, then began to decline leading up to February 11. A total of 1,716 health workers have become infected and 5 have died (0.3%).
Conclusions: COVID-19 epidemic has spread very quickly taking only 30 days to expand from Hubei to the rest of Mainland China. With many people returning from a long holiday, China needs to prepare for the possible rebound of the epidemic.
The Novel Coronavirus Pneumonia Emergency Response Epidemiology Team