The combination of three prominent respiratory viruses this winter – influenza virus, SARS-CoV-2 (which causes COVID-19), and respiratory syncytial virus (RSV) – is raising the risk for older and at-risk adults. But what is it about age that makes some people more vulnerable to infection, and what can we do to reduce their impact?
William Schaffner, MD, is medical director for the National Foundation for Infectious Diseases (NFID), a US organisation that educates and engages the public communities and healthcare professionals about infectious diseases across the lifespan.
“People are using the word ‘tripledemic’ to refer to three prominent respiratory viruses that began their circulation, unseasonably, very early this year,” Schaffner says.
“All of these… are active simultaneously, not to mention that there are other winter respiratory viruses that have not received quite as much publicity.”
Other causes of the common cold, including rhinovirus, adenovirus and human metapneumovirus also pose a threat this season, though it is the “big three” that continue to make headlines – and with good reason.
Since the start of the COVID-19 pandemic in 2020, it’s estimated that 6.6 million people have died worldwide, with nearly 650 million confirmed infections. Prior to the pandemic, the World Health Organization (WHO) estimated that seasonal influenza may result in 290,000-650,000 deaths and 3-5 million cases worldwide each year, while RSV is estimated to account for 29,000 deaths, and 3.5 million cases worldwide each year.
But why do we see greater numbers of cases of these viral diseases when the weather gets colder?
“The easiest explanation, and it’s only a partial explanation, is that winter drives people indoors, closer together, for longer periods of time,” Dr. Schaffner continues.
“And there are several winter holidays that further promote travel, family gatherings, and people once again being very close to each other. These are the exact circumstances that would promote transmission and illness.”
Respiratory viruses are transmitted from person-to-person when people are close to each other for prolonged periods of time. Droplets may spread from an infected person to someone close by (for example, by sneezing), but droplets or aerosols from the mouth and nose can also contaminate items or can linger in the air which then spreads the infection to the next person who touches or inhales them.
“Children are often the great distributors of these viruses in our populations,” Schaffner adds. “They’re together very closely, share these viruses and then they bring them home to their family, particularly older family members.”
Influenza, RSV and COVID-19 all impact the respiratory system – the nose, the throat, and bronchial tubes (small tubes which go down to the lungs). The symptoms – such as runny noses, sneezing, coughing and decreased appetite – are therefore almost identical. In severe cases, these viruses affect the lungs, causing lower respiratory tract illnesses such as pneumonia, or exacerbating underlying conditions, which can lead to hospitalisation and even death.
“Unfortunately, older adults, those generally 65 years and older, are at distinctively increased risk of the complications and are more susceptible to severe disease due to all three of these viruses,” Schaffner says.
One of the reasons older people are more at risk of severe illness from contracting respiratory viruses is immunosenescence - how our immune system weakens with age.
As people age, they are also more likely to acquire underlying chronic illnesses – such as heart disease, lung disease, diabetes, high blood pressure – that predispose them to more severe infections.
In the US, the hospitalisation rate due to all three respiratory viruses is highest among older adults and those with chronic medical conditions. 58,000 children under 5 years are hospitalised from RSV each year, while 100-500 die from the virus. In addition, around 177,000 adults over the age of 65 are hospitalised from RSV each year, and 14,000 die from the virus. For influenza, the figures are fairly similar for adults over 65, with around 140,000 to 170,000 hospitalisations. For COVID-19, around 184,296 adults over 65 are hospitalised compared to 6,138 of children under 5.
“Viruses don’t impact all of us in the same way,” Piyali Mukherjee, Vice President, Head of Global Medical Affairs Vaccines at GSK, says.
“With the majority of infections being mild, there is a misconception that they are like a common cold. But for older adults or those with comorbidities who contract a severe case of flu, RSV or COVID-19, they can be surprised if they aren’t able to shake it off easily, and it can be particularly frightening if they require hospital admission and care.”
So how can people protect themselves – and their loved ones – from severe illness?
“Fortunately, there’s a little sunshine in this dark picture, and that sunshine is of two types,” Schaffner explains.
“The first is vaccines. Vaccines clearly assist in the prevention, particularly in the most serious aspects of both influenza and COVID-19. Vaccines are critical [to public health].”
Global guidance for the vaccination of children has led to reductions in the spread of infectious diseases. For example, vaccinations to protect children against measles resulted in a 73% drop in deaths from the disease between 2000 and 2018 worldwide. Meanwhile, adult vaccines are becoming more common. A recent report from Vaccines Europe (Pipeline Review 2022) highlighted that 80% of 100 upcoming vaccine candidates from their members specifically target the adult population.
“Vaccines have been available for adults for some time,” Dr. Schaffner says. “Although most people are generally aware that infants and young children should receive a series of vaccines, we need to increase awareness about vaccines for adults. By getting vaccinated you help protect yourself and may also extend some of that protection to your family, your neighbours, and your communities.”
Dr. Phil Dormitzer, Global Head of Vaccines R&D at GSK, says that, although vaccines are not guaranteed to prevent infection, “they play a vital role in protecting the health of global populations from seasonal respiratory virus illnesses and, importantly, the ability of health care systems to function during the winter months.”
"Healthcare providers are the best resource for disease prevention information and can advise individuals on the benefits and risks of vaccines and what may be recommended for them,” he says.
Dr. Schaffner’s second recommendation for helping to protect against respiratory viruses is to practice health habits on an individual level.
“We can be more attentive to hand hygiene, we can try to avoid people who are coughing and sneezing, and we can stay home when we are sick. If you are in a high-risk group, you may want to wear a mask if you are going to an indoor group function. You might also want to practice social distancing if you know that there’s an outbreak in your community” he concludes.
“If we do become ill, we can contact our healthcare provider, particularly if we’re in one of these high-risk groups. [But] if you have any kind of questions, always it’s recommended to speak to your healthcare provider. Have that conversation.”
NFID has information about RSV, flu, and other infectious diseases available on their website, www.nfid.org