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Malaria in the United States is almost entirely imported: **2,078 confirmed
cases with onset in 2016**, a 36% increase on 2015 and **the highest
number since 1972.**
The 2015 dip has an explanation — **a decrease in cases from West Africa,
likely from altered travel during the Ebola outbreak** — which is itself a
reminder that these numbers track journeys rather than mosquitoes.
| Where the infections came from | |
|---|---|
| Africa | 1,729 |
| of which West Africa | 1,061 (61.4%) |
| Species | |
|---|---|
| P. falciparum | 1,419 (68.2%) — the one that kills |
| P. vivax | 251 (12.1%) |
| Two species | 23 (1.1%) |
| Not reported or undetermined | 10.8% |
306 cases (14.7%) were severe. Seven people died.
The finding that should change advice
**Of US residents who reported a reason for travel, 69.4% were visiting
friends and relatives.**
Not tourists on safari. People going home — to stay in a family house rather
than a hotel, for weeks rather than days, in a place they grew up and do not
think of as dangerous, and often without a pre-travel clinic visit because the
trip is not felt to be that kind of trip.
And the consequence:
| Reported taking any chemoprophylaxis | 26.3% (26.6% in 2015) |
| Did not take, or did not adhere to, a CDC-recommended regimen | 94.0% of 964 with known information |
| Adherence among those who did take it | poor |
**Among 795 women with malaria, 50 were pregnant — and one had adhered to
mefloquine prophylaxis.** One.
41 cases (2.0%) occurred among US military personnel, a group with a
prophylaxis programme, at a proportion comparable to 2015.
Drug resistance in what came back
CDC tested 144 P. falciparum-positive and nine mixed samples for
resistance markers:
| Genetic polymorphisms associated with resistance to | |
|---|---|
| Pyrimethamine | 142 (97.9%) |
| Sulfadoxine | 98 (70.5%) |
| Chloroquine | 67 (44.7%) |
| Mefloquine | 6 (4.3%) |
| Atovaquone | 1 (<1.0%) |
The top and bottom rows are the story of malaria chemotherapy in one table:
the older the drug, the more completely resistance has arrived.
Malaria without travel
Rare, and worth knowing about: **two congenital cases, three cryptic cases,
and one acquired through blood transfusion** in 2016. Malaria can also be
acquired through laboratory exposure and **local mosquito-borne
transmission** — which is why surveillance exists at all, so that a locally
acquired case triggers control measures rather than passing as an oddity.
The honest caveat
**Completeness of key variables — species, country of acquisition, resident
status — was 79.4% in 2016**, up from 75.7% in 2015. About a fifth of the
detail is missing, which bounds every proportion above.
**Worldwide interventions since the early 2000s have been successful; progress
has plateaued in recent years**, the disease remains endemic across much of
the world, and travellers' use of prevention remains inadequate.
*Source: Centers for Disease Control and Prevention, MMWR Surveillance
Summaries.*
Licence: CC0 1.0 (public domain) · Adapted from www.cdc.gov
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