Avian Flu Diary: Denmark SSI Reports Sharp Increase In Pertussis (Whooping Cough) Since May

Denmark SSI - Whooping Cough Epi Chart

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After the emergence of COVID in late 2019, and the broad implementation of pandemic precautions (masks, social distancing, school closures, etc.) in 2020, regular patterns of common (and sometimes no-so-common) infectious diseases abruptly changed.

Influenza was practically a no-show globally in 2020 and 2021, EV-D68 failed to return in 2020 and 2022, and transmission of other respiratory diseases - including RSV, measles, and Whooping cough (see chart above) - declined sharply.

Over the past 18 months - as COVID has subsided and people are once again intermingling - we've seen the return (and sometimes unusual occurrences) of respiratory diseases around the world. A few notable examples:

UK: Unseasonable & Robust Increase In Scarlet Fever/iGAS Cases

CDC HAN #0479: Increased Respiratory Virus Activity, Especially Among Children, Early in the 2022-2023 Fall and Winter

CDC HAN #00473: Severe Respiratory Illnesses Associated with Rhinoviruses and/or Enteroviruses Including EV-D68 – Multistate, 2022

CDC HAN Advisory: Recent Reports of Human Parechovirus (PeV) in the United States —2022

Denmark SSI: `Extraordinary' Summer Spike In RSV Cases

While there is some debate over the mechanisms behind their abrupt, and often atypical return - with SARS-CoV-2 now apparently a permanent fixture and new variants likely to emerge - these types of disruptions are apt to continue for some time.

All of which brings us to a report from Denmark's SSI on the return - after roughly 3 years - of Whooping Cough. Very large outbreaks tend to occur every 3 to 5 years, with the last one reported in Denmark in 2019.

(translated)

Increase in whooping cough in May and June

The respiratory infection whooping cough increased in May and June beyond normal in most of the country. This is shown by new figures from the Statens Serum Institut (SSI).

Last edited on July 5, 2023

SSI has observed an increase in the incidence of whooping cough in Denmark during the months of May and June 2023.

The number of detected cases of whooping cough is usually below 80 to 100 cases per month. But in the month of May, 104 cases were detected, and in June, at least 284 cases were detected.

"Like many other respiratory infections, the incidence of whooping cough has been very low in the period during and after the covid-19 restrictions, and the increase now is therefore even more significant," says department doctor Peter Henrik Andersen from the Department of Infection Epidemiology and Prevention at SSI.

The increase has been seen in most of the country, but especially on Funen the increase is significant.

Whooping cough typically occurs with increased frequency every three to five years. The most recent epidemics of whooping cough in Denmark took place in 2016/17 and 2019/20.

"It is therefore not unusual that there is again an increase in the number of cases. It is still too early to say whether the increase will go away on its own again, or continue to epidemic levels - but you should currently pay extra attention to the diagnosis in both children and adults," says Peter Henrik Andersen.

Read more in EPI-NEWS WEEK 27

Biggest increase among young people

It is especially among the 10 to 19-year-olds that there is an increase, which is normal. But the proportion is currently larger compared to the epidemic in 2019/20.

In June, a death from whooping cough in a prematurely born child of 2 months was reported.

Pertussis vaccination is part of the childhood vaccination program at 3, 5 and 12 months of age and at 5 years of age - protection is estimated to last 5-10 years, and protection among young people is thus expected to be low.

Read more about whooping cough (disease description)

A few (translated) excerpts from Denmark's EPI NOW report.

Week 27 - 2023

Last edited on July 5, 2023

Increase in the incidence of whooping cough

An increase in the incidence of whooping cough has been observed in Denmark during the months of May and June 2023. The number of detected cases of whooping cough per month is usually below 80-100, but in May 104 cases were detected, and in June there were detected at least 284 (preliminary number). Similar to several other respiratory infections, the incidence of whooping cough has been very low in the period during and after the covid-19 restrictions, and the increase now is therefore even more significant, figure 1.

(SNIP)

Whooping cough typically occurs in a cyclical pattern with increased incidence every 3-5 years. The most recent epidemics of whooping cough in Denmark took place in 2016-17 and 2019-20, figure 1 as well as EPI-NYT 46/2016 and EPI-NYT 38/2019 , and it is therefore not unusual that there is again an increase in the number of cases. It is still too early to say whether the increase will go away by itself again, or continue to an epidemic level - but you should currently pay extra attention to the diagnosis in both children and adults.

(SNIP)

The age distribution is with a predominance of young people aged 10 to 19, and this applies throughout the country, table 1.

This predominance of young people is normal, but the proportion is currently greater compared to the epidemic in 2019-20. Pertussis vaccination is part of the child vaccination program at 3, 5 and 12 months of age and at 5 years of age. The protection is estimated to last 5-10 years, and the protection among young people is thus expected to be low. However, whooping cough is particularly serious for infants, which is why the vaccination program is primarily aimed at protecting this age group.

For cases among small children under the age of two, there have been 16 cases up to and including the end of June, of which 12 were under the age of 1. Of the 16 children, 7 were unvaccinated, 3 had received one vaccine, 4 had received two vaccines and 2 had received three vaccines. The more vaccines the child has received, the better the protection, and the greater the likelihood of a milder course of the disease if possible. infection.

A death from whooping cough in a 2-month-old premature child was reported in June, see below. Deaths due to whooping cough are rare in Denmark and were last reported in 2010, EPI-NYT 42-43/2011 .

(Continue . . . .)

While this uptick appears to be limited to Denmark right now, Denmark was one of the first countries report a post-COVID surge in RSV, which eventually spread to many other countries (including the United States).

As summer is often Whooping cough season, parents may want to make sure their kid's vaccinations are up-to-date. And while children and adolescents are most commonly affected, anyone of any age can become infected.