Infection preventionists (IPs) are preparing for an unknown but widely predicted possibility this fall and winter: a large second wave of SARS-CoV-2 (COVID-19) hitting hospitals amid the 2020-2021 influenza season.

“It’s sort of a nightmare scenario if and when the two collide and converge on us at the same time,” says Ann Marie Pettis, RN, BSN, CIC, FAPIC, president-elect of the Association for Professionals in Infection Control and Epidemiology.

“It makes sense that we would see both at the same time, and that could easily start to overwhelm facilities, which of course was the whole idea of flattening the curve in the first place. We are hoping for the best and preparing for the worst.”

Although the outcome remains unknown as the global pandemic continues, leading epidemiologists say this respiratory viral confluence is a distinct possibility.

“I am deeply worried that, as we get into the fall and winter, we are going to be hit by a very large second wave that is going to coincide with influenza season,” said Ashish Jha, MD, MPH, director of the Harvard Global Health Institute in Boston, in a recent webinar. “That is going to substantially strain our healthcare system, eventually set in, and kill a lot of people.”

Outspoken about the need for more testing since the pandemic began, Jha was skeptical about Department of Health and Human Services (HHS) projections of more COVID-19 tests during flu season.

“Forty to 50 million tests a month sounds a like a big number, but that is about 1.5 million tests a day. While that would be a dramatic improvement over where we are right now, it is hard for me to see [that being sufficient] in the middle of an influenza season and what we expect will be an increasing number of [COVID-19] cases.”

However, Jha is hopeful that a shift to new tests will bolster the current, widespread use of reverse transcription polymerase chain reaction (RT-PCR).

“I don’t believe that our primary testing strategy in the fall will be RT-PCR,” he said. “I think it will be an important component of it, but I suspect and hope that antigen testing, maybe next-generation sequencing, and some of the [genomic] technologies that are coming out will be available and represent the bulk of the testing. Because I think reagents and other supply chain issues are going to become a limiting factor once you get above about a million tests a day for RT-PCR."

The interaction between flu and novel coronavirus in the Southern Hemisphere may foretell what the United States will face this fall and winter, he said.

Flu Vaccination Critical

“One of the main messages IPs need to get out there is the importance of flu vaccination,” says Pettis, director of infection prevention at the University of Rochester, NY. “The symptoms can present pretty similarly with the two diseases, so it could be difficult to sort out. But we have learned a lot of lessons dealing with this pandemic — we have seen a lot of positives. I’ve been doing this a long time and I have never seen such good teamwork and camaraderie among healthcare providers and staff.”

Although the hospital does not have a mandatory flu shot policy, Pettis and colleagues will emphasize boosting a voluntary vaccination rate that is already in the high 90th percentile.

“I think healthcare workers have gotten the message and are doing very good with that, but there is still not as much public uptake as we are going to need,” she says. “We are going to be advocating for public messaging and public service announcements for health departments. We don’t have a treatment or vaccination for COVID yet, but the things that we can do are flu vaccination and emphasizing the basics of infection prevention, which IPs have been doing on the front lines throughout this.”

William Schaffner, MD, one of the nation’s leading vaccine proponents, says the message of a “double-barrel” viral season will be emphasized in public messaging that probably will begin in late summer. That includes the Centers for Disease Control and Prevention (CDC) and the annual flu press conference Schaffner leads at the National Foundation for Infectious Diseases in Washington, DC.

“With flu and COVID — not to mention RSV (respiratory syncytial virus) and all the other viruses — we fear a great surge of patients coming into the healthcare system,” says Schaffner, professor of preventive medicine at Vanderbilt University in Nashville. “At the moment, flu vaccine is the best intervention we have — not only to provide individual protection, but to mitigate the impact and very substantial demand for medical care.”

As the novel coronavirus began to emerge globally, more flu testing was done at U.S. hospitals to make sure COVID-19 was not missed, says Monica Gandhi, MD, MPH, an infectious disease physician at the University of California San Francisco.

“A good thing about this last flu season is that we have done more flu testing than ever before,” she says. “We were testing for both SARS CoV-2 and influenza, so we know the strains out there. We should be able to create a really good flu vaccine this year.”

For the 2019-2020 flu season, the CDC has released preliminary estimates of a range of 410,000 to 740,000 hospitalizations and 24,000 to 62,000 deaths.1

“We just came off a horrific flu season just as COVID was ramping up,” Pettis says. “We were already seeing patients in corridors and so forth, and that was before we really hit our stride with the pandemic. It could be a rocky ride.”


In that regard, triage tents are being left up at the hospital, an outward sign of vigilance, even though the novel coronavirus has declined from its peak in the area.

“We are still seeing it in the community, but in the ICUs, what we are seeing now is a surge of folks that were afraid to come in for care [during COVID-19],” she says. “We are seeing a surge of things that we normally deal with. But we are still in emergency command mode as we speak, and my sense is that will continue.”

In the pause in the viral surge, preparations for the next wave continue. “IPs are still constantly educating about appropriate donning and doffing of PPE (personal protective equipment) and that will continue,” she says. “We are still auditing and working with them to make sure they remember, [because of] the fatigue, as you can imagine, that they have in wearing all the face shields and masks. So, I do worry about that. It is something, as IPs, we must constantly assess.”

The ebb and flow of testing materials, PPE, and other supplies has been a “constant dance,” she says. “As recently as last week in our area, we had issues with our reagents. It’s been a day-to-day fight.”

Pettis and colleagues are ramping up antibody testing for SARS-CoV-2 and will offer that to healthcare workers who want to be tested. “We are still doing the PCR testing for actual infection.”

Rapid flu tests will be used when the season hits because testing before influenza is circulating in the community could lead to false positives. “We do a rapid flu test, but until flu is really prevalent in your community you can have false results on the rapid test. It is a good tool in terms of triaging, but it is certainly not foolproof.”

All admitted patients are being tested for COVID-19, and because of the possibility of asymptomatic transmission, healthcare workers must wear a mask and eye protection throughout their shift. Patients with confirmed coronavirus also must don a mask when healthcare care workers come into their rooms. Pettis, who worked in Toronto during the SARS outbreak of 2003, said universal public masking may become common even after the pandemic ends.

“I think many of us in healthcare have sort of pooh-poohed the idea of using masks in public as source control,” she says. “I think that is going to become a new normal, and moving forward, we are probably going to be emphasizing that more as an effective means of source control. I won’t be surprised even after [COVID-19] if we will see more and more experts recommending public masking for source control during increased incidence of flu.”

Universal Public Masking

Emerging data show that widespread public masking could tamp down infections and particularly lower mortality, Gandhi says.

“The CDC recommended universal masking April 3, and many cities have opened and followed suit,” she says. “I think it is going to save us from a second wave. I am profoundly hopeful of that when I look at other countries. The most effective measure, as they open up, to prevent resurgence is universal masking.”

Gandhi cites a study of a coronavirus outbreak on a cruise ship where all passengers were issued surgical masks.2 It was found that 81% of those testing positive for COVID-19 remained asymptomatic. In a paper in press, Gandhi and colleagues propose an “inoculum” theory hypothesizing that masks lower the viral dose emitted and received in a setting of a universal masking.3 It is well-established that a mask acts as source control, protecting others from the wearer.

“But there is a second benefit that has received less attention,” Gandhi and co-authors note.

“Exposure to a lower inoculum or dose of any virus (whether respiratory, gastrointestinal, or sexually transmitted) can make subsequent illness far less likely to be severe. Increasing rates of asymptomatic and mild infection with COVID-19 seen over time, in the setting of masking, supports this theory.”

In Asian countries where public mask wearing is a cultural norm, lower rates of COVID-19 mortality are being documented, the authors emphasize.

“While there is some correlation between universal masking and number of COVID-19 cases, there is a near-perfect correlation between public masking and suppression of COVID-related death rates,” they conclude. “Case fatality from COVID-19 is universally low in regions with universal masking.”

There has been confused messaging and political divisiveness on this issue, with the initial rationale that mask wearing is to protect others. Gandhi argues that in a public setting, surgical masks may afford the wearer some protection by lowering the viral inoculum inhaled.

“The beginning message was that it protects others, but in a society that has not exactly been altruistic — especially in the current climate — that has not been the most effective way to convince people to wear masks,” she says. “The message needs to be that masks protect both — it protects others and it protects you as well. It makes sense that it would protect you. You can’t contract it directly through your skin — you get it into your body through your mouth or nose. Wearing a mask also protects you from touching your mouth and nose.”

Mask-wearing in public is not a cultural norm in the United States, she concedes, but notes that neither is mass isolation of people in their homes.

“We have figured out a lot about this virus in the last few months,” she says. “Before it was ‘radioactive’ — can you touch a surface and get it? We [know] that it is shed from the nose and mouth. That makes it so simple in a way — all you have to do is cover the nose and mouth.”

There could be some benefit if any resulting infection is mild or asymptomatic, particularly if it is found that such cases develop immunity and thus increase protection of the herd.

“As the economy opens up, universal masking may not prevent exposure but potentially lead to only mild disease,” Gandhi and colleagues state. “One model found that, if 80% of the population wears a moderately effective mask, nearly half of the projected deaths over the next two months could be prevented.4 That means less illness, fewer deaths, and a safer reopening of society.”


  1. Centers for Disease Control and Prevention. 2019-2020 U.S. flu season: Preliminary burden estimates. April 17, 2020.
  2. Ing AJ, Cocks C, Green JP. COVID-19: In the footsteps of Ernest Shackleton. Thorax 2020; May 27. [Online ahead of print].
  3. Gandhi M, Goosby E, Jha A. Universal masking protects the wearer and your neighbor: The inoculum theory. June 2020. In press.
  4. Kai D, Goldstein GP, Morgunuv A, et al. Universal masking is urgent in the COVID-19 pandemic: SEIR and agent based models, empirical validation, policy recommendations. Cornell University. April 22, 2020.