Professor Shabir A Madhi on the flu & Covid-19
WHAT ARE THE SIMILARITIES BETWEEN SARS-COV-2 WHICH CAUSES COVID-19 AND THE INFLUEZA VIRUS?
What is similar between the two is their mode of transmission between individuals, the time of the year when they most likely to circulate in the country (autumn and winter months), and the clinical manifestation of initial illness (i.e. non-specific symptoms of cough, fever, runny nose, muscle ache, headache and chest pain). People with COVID-19 may also have reduced sensation of smell and taste, which is less common with influenzae virus
Both of these viruses are spread by respiratory droplets. It is through those contaminated droplets when individual come into contact with it and inadvertently touch their hands and face and mucous membranes that they might infect themselves. Also, a person may become infected by an infected- person transmitting their contaminated droplets directly onto mucus membrane surfaces (e.g. eyes, mouth and nose) of an uninfected person. That is the reason why physical distancing is so important, to avoid this sort of accidental exposure that could take place even when only talking to an infected person who is not wearing mask. More recently, there is also evidence that tiny droplet particles containing the virus may be present in the air for a brief period, which could possibly be inadvertently inhaled and result in infection of another person in the same proximity.
The other similarity between the two is the clinical manifestation in terms of how it presents; after an individual is infected the virus starts replicating before starting an illness in the individual. Not everyone infected who is infected by the virus ends up becoming sick, in fact up to 50%-80% of people infected with seasonal influenza virus as well as with SAS-CoV-2 s might be completely well and they would never know that they were actually infected. Now what about the other 20%-50% of people that become ill because of infection with SARS-CoV-2? So it will start of as a mild respiratory illness, a runny nose, a cough and then it might go on to develop a fever. The majority (85% of those with some symptoms) of people that develop those signs of symptoms in fact would recover on their own. It is what we call a self-limiting illness. The body is able to mount an immune response against the virus and you able to clear the infection completely. Similar to influenza virus (except for young children who don’t usually develop severe COVID-19 illness) there is a part of the population that are at increased risk of developing severe disease. These 12 to 15% of people who have got underlying medical conditions will develop a severe illness and unfortunately are also more likely to die. The adults at high risk for severe disease include the elderly (>65 years age, those with chronic lung or chronic lung disease, those with hypertension, underlying cancer as well as people with diabetes. In addition, adults with poorly controlled diabetes and those who smoke may also be at increased risk of severe COVID-19. Once those people become ill, they may develop pneumonia, which could manifest with chest pains and difficulty with breathing. Also, because they unable to get enough oxygen into their blood they might need additional support up to the point of possible needing to be admitted to ICU for mechanical ventilation.
CAN THE FLU VACCINE PROTECT ME AGAINST COVID-19?
The flu vaccine is important to get, but will not protect you directly against COVID-19, as the vaccine is aimed at stimulating an immune response to the influenza virus rather than to the SARS-CoV-2. The reality in the South African right now is that there are roughly over seven million people that are considered to be high risk for severe influenza illness including people that are living with HIV, the elderly, people with heart conditions, lung conditions, etc. The flu vaccine is designed to prevent or reduce the risk of an individual becoming infected with seasonal influenza. If people get immunized against flu now. It’s not going to give you 100% protection and I need to be clear about that. Rather, the protection that the flu vaccine gives you is about 50 to 75% in most years. But if people get vaccinated now what we going to prevent in South Africa is that when there is an upsurge in COVID-19 cases in the community, which is likely to occur in winter together with the increase in illness from influenza virus, at least preventing people from needing to be hospitalised for influenza illness (by getting vaccinated), it will assist in lessening the pressure in our health care facilities; and create a space to allow for the additional cases of hospitalization that is expected from COVID-19 cases.
CAN YOU SPREAD COVID-19 IF YOU ARE ASYMPTOMATIC (INFECTED WITH NO SYMPTOMS)?
Recently, we have found out that as many as 50-80% of people infected with SARS-CoV-2 are asymptomatic. There is emerging evidence that these people, as well as those who develop illness but prior to them actually developing symptoms (i.e. pre-symptomatic phase) could be responsible for transmitting the virus in the community.
After getting infected with the virus there is what we call an incubation period. That incubation period means the virus is replicating at the back of the throat, in your pharynx and you would be completely unaware to it, but it’s replicating there (i.e. this is the pre-symptomatic phase of infection in those who do become ill). But it is when the immune system mounts an immune response against the virus or when the virus is causing damage to the airway mucosa that the person becomes symptomatic. When that happens, there is also an increase in the density of the virus. For you to become efficient in transmitting the virus it depends on the density – the amount of virus that you actually have at the back of your throat. Because that is going to determine how much of your droplets are going to be infected and how much you going to contaminate the environment or are a risk to infecting others. So there is a possible that asymptomatic and pre-symptomatic individuals might actually also be spreading the virus.
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