Health officials in certain areas of the UK have issued a warning after cases of the '100 day cough' have seen a sharp rise across Britain.
The highly contagious disease - also known as whooping cough - has seen an increase in Wales especially.
Whooping cough is highly contagious and can be very serious in babies and young children.
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The cough is caused by a bacterial infection of the lungs and breathing tubes.
It can be particularly concerning in young babies under six months of age, which is why pregnant women are offered the whooping cough vaccine from 16 weeks gestation.
A following vaccine is included in a baby's routine jabs once they are eight, 12 and 16 weeks old.
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Whooping cough can last for several weeks or even months, with the NHS explaining that hospital treatment is often needed if you develop severe whooping cough, or in babies under six months.
Data from UKHSA reveals that between July and November 2023, there were 716 suspected cases of whooping cough in England and Wales, compared with 217 the year before and 213 in 2021.
Meanwhile, there have already been 135 cases so far in January of this year.
Public Health Wales expert Dr Chris Johnson believes the figures are the start of a relatively large wave.
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He has urged all pregnant women, as well as parents of babies and young children, to ensure they are vaccinated.
The consultant epidemiologist added: "With rates suppressed during the lockdowns of the pandemic we are naturally seeing a resurgence this year.
"... It can be very serious and lead to pneumonia and permanent brain damage. "Young babies with whooping cough are at risk of dying from the disease."
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It comes as another disease, measles, has also seen a sharp rise in recent months.
Health officials are urging for national action following the increase in children coming down with the illness.
Professor Dame Jenny Harries, chief executive of the UK Health Security Agency (UKHSA), has urged parents to check if their kids have had the measles, mumps and rubella (MMR) jab.
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Some 216 confirmed measles cases and 103 probable cases have developed in the West Midlands, including 80 percent of cases in Birmingham and 10 percent in Coventry.
Most of the children who have been affected are under 10-years-old.
Between 2022 and 2023, around 84.5 percent of young people in England had received both doses of the jab by the time they were five years old.
Although that sounds like a lot, it's the lowest level since 2010/11.
Topics: Health
Lucy Devine