Study shows lower case-fatality rate in COVID-19 second wave

A new study in Transboundary and Emerging Disease calculated the case-fatality rate (CFR) of COVID-19 infections in 53 countries or regions that experienced a second wave—or resurgence—of coronavirus activity, and found a significantly lower death rate among all confirmed cases than in the first wave.

This is the first study to compare the CFR in the first and second waves of the pandemic. 

Researchers from Hong Kong based the study on daily confirmed COVID-19 cases and deaths for 216 countries or regions, during February of 2020 through August 2020, and weekly influenza confirmations during 2015 to the current week of 2020, from the World Health Organization (WHO). They defined the first wave as cases before Jun 1, and deaths before Jun 10, and second wave as any case after Jun 1 or any death after Jun 10.

Forty-three of the 53 regions studied showed lower CFRs during the second wave than the first. The 10 countries or regions with higher CFRs in the second wave were mostly in the Southern hemisphere (eg, Peru, Chile) and had reported mild first waves of the pandemic.

The authors offer possible explanations for the higher CFR in the first wave, including a harvest effect, where the elderly and infirm were first infected. They also said countries improved testing and surveillance, which helped them record more mild cases. Finally, they said younger people were more likely to be infected in subsequent waves and were less likely to die from infections.

Flu data from the WHO also showed steep declines in flu transmission during both waves, a sign that physical distancing measures reduced influenza spread.

“Although the lower CFR in the second phase is a positive sign to suggest the decrease[d] severity of COVID-19 infections, the shift to younger age groups could bring more difficulty in containing the pandemic,” the authors concluded. “We also need to stay vigilant for the potential rebound of influenza outbreaks as many countries or regions are planning to lift social distancing control measures.”
Sep 6 Transbound Emerg Dis study

 

Groups emphasize pandemic risk for Chinese swine H1N1 flu subtype

Three global health groups today issued a joint statement that strongly urged countries to be aware of the pandemic potential for an H1N1 swine influenza subtype circulating in Chinese pigs. The statement is from the United Nations Food and Agriculture Organization (FAO), the World Organization for Animal Health (OIE), and the World Health Organization (WHO).

The 1C.2.3 (“G4”) genetic clade of H1N1 swine influenza was first identified by Chinese researchers in 2016 and has become the dominant genotype circulating in China’s pigs. Two variant H1N1 cases involving the subtype have recently been detected in humans, and a small seroprevalence study in Chinese swine workers suggested that 10% had been exposed to the virus. The WHO Collaborating Center in China has developed a candidate vaccine virus targeting the strain.

Keith Sumption, DVM, PhD, the FAO’s chief veterinary office, said though there are limited data on human infections and circulation of the virus in pigs, heightened awareness is needed for a number of reasons, including a recent study from China showing that the virus has characteristics linked to increased ability for zoonotic transmission.

“The viruses have some genetic markers to suggest human infection is possible; they can replicate in human airway cells, and viruses can be spread via respiratory droplets passed between ferrets,” he said.

The group urged countries to rapidly assess and share their latest surveillance data.
Sep 9 FAO, OIE, and WHO statement

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