US national public health agency, the Centers for Disease Control and Prevention, this week rolled out a new influenza A wastewater surveillance dashboard to better ascertain where H5N1 (a subtype of influenza A) might be spreading.

As at 4th May, influenza A virus was detected in higher-than-average levels in Alaska, California, Florida, Illinois and Kansas, amongst other states.

Wastewater surveillance aside, gaps in testing animals and people for the virus may be obfuscating the real rate of avian flu infections in the US, making it a challenge to gain a full understanding of how the virus is spreading and how to best respond.

Outbreaks of H5N1 avian influenza amongst dairy cows have thus far been reported in nine US states, with 46 herds affected, according to the Johns Hopkins Center for Health Security, with the US FDA this week reiterating its warnings against consuming raw milk and raw milk products.

Without pasteurisation, raw milk could contain viable H5N1 virus, it has warned. Despite this, some raw milk advocates insist that drinking raw milk will give them immunity to the virus, which the US FDA has said is “highly unlikely”.

The US government last week said it has designated nearly US$200 million for states to restrict the interstate movement of affected cattle and for expanded surveillance, testing, treatments and vaccines for H5N1.

"The concern is that some strains of avian influenza will have or develop the capacity to spread efficiently between humans in the manner of the 1918 H1N1 influenza pandemic, which was an avian-origin influenza virus,” Center for Health Security senior scholar Dr Amesh Adalja, said.

Meanwhile, several new SARS-CoV-2 Omicron subvariants, including KP.2, JN.1.7 and other KP and JN variants (a group that is also referred to as ‘FLiRT’ variants), are now responsible for the majority of sequenced Covid-19 cases in the US.

Whilst there are concerns that the latest Covid vaccine boosters may not provide strong protection against the FLiRT variants, recent infection with JN.1 should provide strong protection against all of them, until immunity wanes, the Johns Hopkins Center for Health Security said, adding that low levels of SARS-CoV-2 transmission overall do not point to an impending summer wave of Covid-19.

Covid-19 continues to cause waves of disease in England, where similar concerns about the effectiveness of vaccinations against the dominant sub-lineage, JN.1, persist. JN.1 accounted for 85% of sequenced cases in the country by late January 2024, according to the UK Health Security Agency's National Influenza and Covid-19 surveillance report from week 9.

Given recent reports relating to the AstraZeneca vaccine, readers looking to explore in-depth data on the efficacy of Covid-19 vaccines in England may find these pages of interest: https://www.gov.uk/guidance/monitoring-reports-of-the-effectiveness-of-covid-19-vaccination

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